Fig. 54.—Chondromyces apiculata, one of
The Myxactabacaea. A., young, B. mature
Mycelium. C., spore-cell. D., spore-cell,
very much enlarged.
Rather common in fresh water
(From Hustedt).
Distribution.—Like
the Bac- teria, these plants are widely distributed, and are adapted
to extremely varying conditions. While they are for
the most part aquatic, many of them grow on moist earth,
or upon wood and rocks in shady places. Like
the Bacteria, also, many of them can endure drying up for long periods without injury. They are abundant
both in fresh and salt water;
and in some cases they may occur in enormous quantities in open sea,
or in lakes and ponds. The red color
of water near shore is due
to enormous floating masses
of these plants—*Trachelomonas*.*—(From Hustedt).
Distribution.—These plants are found in fresh water,
sea, and other warm parts
of ocean.*—(From Hustedt).
Schizophyceae are among
the principal plants in hot springs,
and many
of those that occur abundantly in water charged
with various mineral salts. Many
of these are patho-parasites;
i.e. they grow associated
with other plants,
without, however,
apparently doing any harm
To the host. Thus
The little Water-fern,*Azolla,*has always associated
In it some form, *Anabaena azollae*,
"e.g." Anthoceros and Blasia. Among the Seed-plants, Cycas
+
+80
+BOTANY
+
+Guinerae have a Nostoc associated with them, and many of the Lichens have species of Schizophyses forming their "genia." This habit of associating themselves with other living organisms, as well as their frequent preference for water containing organic matter, indicates a certain dependence on organic food which is not found in the higher green plants.
+
+**Structure of Schizophyses**
+
+The simplest forms among the Schizophyses are unicellular, but more commonly the cells are united into filaments of definite form. The cells are either approximately globular, e.g., Nostoc, Chlorococcus, Anabaena, or they are cylindrical or flattened, e.g., Chroococcus. There has been much discussion as to the structure of the cell, and there is still more or less difference of opinion concerning the nature of some of the structures. Some Schizophyses live isolated, but usually they occur in large masses.
+
+The Cell-wall. — The cell-wall is thin, but is more commonly thick and gelatinous, seldom showing the reaction of pure cellulose, but usually resembling more the cutinized membranes of the higher plants. It is often colored yellow, or sometimes blue-green. In some cases it is not visible at all. In these, the plasma is imbedded in large gelatinous masses, derived in part from a change in the cell-wall, but probably, for the most part, a direct secretion of the cells. Like the cell-walls of higher plants, such they much resemble, there are of characteristic form and color in each species.
+
+The Protoplast. — In the larger Schizophyses the protoplast usually shows a more or less distinct boundary between it and the cell-wall. The protoplast is confined, and a central colorless part, the central-body, which is often irregularly in outline. The protoplast contains a nucleus (nucleus), which may be represented by a rudimentary nucleus, but this has been disputed. The chlorophyll (which is associated with a blue pigment (phycoerythrin)), is confined to the peripheral cytoplasm. In some species (e.g., Nostoc) there is no chlorophyll whatever; whether there is a special chromatophore, is not agreed upon. A definite chromatophore can certainly be detected in the young heterocysts of Anabaena (see Fig. 6d), and it seems probable that it also exists in other species. In some species it is absent. At least granules may generally be seen in the proplast, and those it is claimed are of two kinds, the so-called Cyanophycos-granules, which are confined to the periphery of the protoplast, and the so-called Chlorophycos-granules, which belong to the central-body, and are probably allied to the chromato-gen- ules of a higher plant.
+
+**Pigments.** — The Schizophyses contain, in addition to the chloro- phyll, a second pigment, usually a blue one (Phycoerythrin), but sometimes a violet or orange-yellow modification of this pigment. The phycoerythrin is readily soluble in water, and in drying speci- mens for photography it often makes a bright blue stain on the paper. The extract obtained by boiling with alcohol on filter papers specimens in water appears pure blue if seen by transmitted light, but by reflected light it shows a marked purplish red fluorescence. The
+
+CLASSIFICATION 81
+
+residue, after the phycocyanin is extracted, yields a green solution if treated with alcohol, but this solution is usually tinged with brown on account of the mixture with phycothallin. The phycocyanin may be precipitated from the juice of blue crystals by the action of ammonium-sulphate.
+
+**Vacuoles.** — Vacuoles are usually absent from the vegetative cells, but occur in the heterocytos. Vacuoles filled with gas, which render the cells buoyant, are found in those species which float at the surface of the water.
+
+**Differentiation of the Plant-body**
+
+The lowest of the Schizopyleae, the Chroococcaceae, are strictly unicellular forms, which live either isolated or in colonies. The cells divide by transverse fission, although secondary divisions may follow before the cells have become completely rounded off. The cell-wall is usually gelatinous, and often striated.
+
+The other forms are mostly filamentous. In the Oscillariiferae, the lowest order, the cells are short-cylindrical, but all alike, except that the tip of the filaments is often somewhat attenuated. In the Heterocytos, the cells are rounded, and in addition to the ordinary cells, so-called "Heterocytos" are formed, sometimes at irregular intervals, as in Noctea and Anabena; sometimes at definite place, as in Cylinodispernum (Fig. 65). These "Heterocytos" are derived from the ordinary cells by their losing most of their protoplasmic contents, and becoming enlarged, with thickened, usually yellowish, cell-wall. In young heterocytos the chromatophore may sometimes be seen within the cell-walls. When mature, however, the heterocyst is shut off from the adjacent cell by a sort of plug, which projects into its cavity. The heterocytos serve to separate the "Homogonia" or segments into which the filaments finally separate. (The Noctecae may also develop thick-walled resting spores (Arthrospores).)
+
+![]() A: A four-cell colony of Chroococcus turgidus, surrounded by its gelatinous sheath.
+![]() B: A single cell containing resting spores (Arthrospores).
+![]() C: A single cell containing resting spores (Arthrospores).
+
+82
+BOTANY
+
+In the Seytonemataceae (Fig. 56, E) the filaments branch, and in the Rivulariaceae (Fig. 58), the filaments are much attenuated and have a single base. The cells multiply by simple cell-division, which is accomplished by the formation of a ring-shaped wall at the equator of the cell, which grows inward and gradually cuts the protoplast in two. This process, apparently, is quite invasive, and takes up a large part of the cell-lumen. In Chamaesiphonaceae, internal cell-division has been observed, resulting in the formation of numerous "conidia" (Fig. 55, C).
+
+![]() A small diagram showing a filamentous organism with a central body in each cell.
+
+**Reproduction**
+
+In the Chlorococcaceae (Fig. 55, A) there is no distinction between vegetative and reproductive cells, each cell-division resulting in the formation of two individuals. In the filamentous forms there is usually a breaking up of the filament into two parts, one of which remains attached to the other, or out of the sheath or gelatinous envelope in which they are enclosed. In case heterocytes are present, they become detached, leaving portions of the filament lying free within the sheath or gelatinous envelope until from the beginning of a new plant or colony. It is in this condition that they usually infect the plants with which they may be associated.
+
+Resting spores are formed in some species. These are formed by a simple enlargement of a vegetative cell, or occasionally, e.g. Rivularia, apparently by a simple division of the protoplast. The walls of the resting spore become very dense by the accumulation of reserve-food, and a thick wall is developed about it. The spore may be formed from almost any cell in Nostoc and Anabaena, but in certain genera like Cyanothecum and Rivularia they occupy a definite position in the filament.
+
+![]() C B D E h-h
+
+CLASSIFICATION 83
+
+The arthrospores are more resistant than the vegetative cells, and remain after the rest of the plant is dead. On germination (Fig. 57, F, G) the contents of these cells are liberated, and the spore divides into two or three parts, which grow out once or twice by transverse walls, and the outer spore-membrane is ruptured, allowing the contents to pass into the protoplasm. It elongates and grows rapidly until the new plant is complete.
+
+In desiccation, the vegetative cell may enter a resting-stage without becoming completely dry. The protoplasm becomes simply separating and losing most of their color. When growth is resumed, these cells divide while they are again and begin to divide and grow at once.
+
+Movements
+
+None of the true Schizophyceae have cilia, although blue-green motile organisms, e.g. Crypto- monas, do possess them; but these are structurally quite different from the typical Schi- phyceae. Goebel, however, mentions that the "bacterium-like" motile cells in process of fission. F., germi- nating spores of Cylinodropernum.
+
+The most striking movements are those of the Oscillatoriaaceae. Oscillatoria is one of the commonest of the Schizophyceae, abound-
+
+![]() A diagram showing a plant with a long, thin stem and a round bulbous base.
+![]() B Diagram showing a plant with a long, thin stem and a round bulbous base.
+![]() C Diagram showing a plant with a long, thin stem and a round bulbous base.
+![]() D Diagram showing a plant with a long, thin stem and a round bulbous base.
+![]() E Diagram showing a plant with a long, thin stem and a round bulbous base.
+![]() F Diagram showing a plant with a long, thin stem and a round bulbous base.
+![]() G Diagram showing a plant with a long, thin stem and a round bulbous base.
+
+Fig. 57. — A, B, C, Cylinodropernum coturnicum; sp., spore; h., heterocyst; E., branching filament; F., germi- nating spores of Cylinodropernum.
+
+A
+B
+C
+D
+E
+F
+G
+
+Fig. 58. — A. leaf of Myriophyllum with colonies of Gloeotrichia notata, slightly enlarged. B-D. development of the spore (x 400). E., branching filament; h., young heterocyst.
+
+ing in every fresh-water pool, and its movements have been repeatedly studied, but are still not clearly understood. The slender
+
+84
+BOTANY
+
+filaments show active swaying and revolving movements, and when in contact with a solid substratum, they creep about actively, soon spreading themselves in a film with the free ends of the filaments radiating from the centre of the mass (Fig. 56, A). The hormogonia of Nostoc, and other forms which do not usually exhibit movement, often show for a time, active creeping movements by means of which they escape from the gelatinous envelope and seek a new spot to establish themselves.
+
+**Classification of Schizophyceae (Kirchner, 8)**
+
+Schizophyceae (Blue-green Algae)
+
+Ord. I. Cococcaceae.
+a. Reproduction by simple fission. Fam. 1. Chroococcaceae.
+b. Reproduction by conidia. Fam. 2. Chamaesiphonaceae.
+
+Ord. II. Hormogoneae.
+Multiplication by cell-rowa (hormogonia) which often show creeping movements. Simple or branched filaments, often with sheath or gelatinous envelope.
+a. Simple filaments of cylindrical cells, no resting-spores or heterocytes. Fam. 3. Oscillatoriaceae.
+b. Usually round cells, heterocytes, and often arthrospores. Fam. 4. Nostocaceae.
+c. Filaments enclosed in sheath, showing false branching, usually showing base and apex; heterocytes and resting-spores usually present. Fam. 5. Scytonemaceae.
+d. Filaments enclosed in sheath, showing true branching; branches often attenuated; heterocytes and arthrospores sometimes present.
+e. Filaments much attenuated with basal heterocyte; arthrospores sometimes present. Fam. 7. Rivallaciaceae.
+f. Filaments epiphytic, tapering at both ends; no heterocytes or arthrospores. Fam. 8. Camptosiphonaceae.
+
+**PERIDINIEAE (PERIDINALLES) (SCHÜTT, 18)**
+
+Among the important constituents of the surface life (Plankton) of the ocean, and to a lesser degree of fresh water, are numerous unicellular organisms whose affinities are not very clearly understood, but which show evidences of their plant-nature. The most impor-
+
+CLASSIFICATION 86
+
+tant of these are the Peridiniae and the Diatoms. These organisms, although of minute, often microscopic, size, are of enormous importance, as they are the principal green organisms of the plankton, and are the original source of food for nearly all marine animal life.
+
+Structure of Peridiniae
+
+The Peridiniae (Fig. 50) show much resemblance to some of the Flagellata, with which they are probably related. Like them, they are provided with two flagella, which are, however, usually inserted laterally. They generally show membrane-division, but this is more marked in the more specialized forms composed of a number of scutate plates joined together by a low order, Gymnodiniaeae, are either naked cells, like most Flagellata, or covered by a thin cell-lining or grattinous membrane. In the higher forms, such as the Volvox, a division into two valves or pieces which fit together, and in this respect they resemble much resem-
+ble the Diatomaceae.
+Some of the Peridiniae are desti-
+nate of being green, while others are usually present. They may be pure green, or there may be prussacene yellow pigments present as in the Diatoms, this being especially the case with some of the Gymnodiniaeae.
+
+Reproduction. - Reproduction is principally by simple fission, but occasional cases of budding have been observed. The zoospores or motile reproductive cells by internal cell-division. No sexual reproduction has been observed, but it is probable that it exists.
+
+Distribution. - The Peridiniae are most abundant floating on the surface of the sea, and are found in great numbers in fresh water also. E.g. Ceratium tripos, are joined in chains, but more commonly they are isolated cells.
+Some of the Peridiniae, like *Pyrocystis noctiluca*, are among the impor-
+tant planktonic organisms.
+
+Affinities of Peridiniae. - The Peridiniae are probably related to the Flagellata, but they also show resemblances to the Volvocacea,
+the lowest of the Green Algae, and also to the characteristic group of Seaweeds, the Brown Algae. The zoospores of the latter are strikingly similar to those of the Peridiniae brown algae. In their coloration and structure of the membrane, there is a suggestion of the Diatomaceae.
+It seems likely, then, that the Peridiniae are a very primitive group of organisms, with affinities in several directions.
+
+![]() A diagram showing a cross-section of a peridinium cell.
+A B C
+
+Fig. 50. - A. Hemidinium caudatum (x 300). B. *Pyrocystis* noctiluca (x 300). C. *Pyrocystis* hawaii (x 300). A., after Scutt.; B., C., after Scutt.
+
+50
+
+96
+BOTANY
+
+**Classification of Peridiniae (Schütt)**
+
+A. Cells naked, or with continuous membrane. Ord. I. Gymnodiniaceae.
+B. Membrane composed of two pieces. Ord. II. Procorestraceae.
+C. Membrane composed of several plates, arranged in two groups, or valves. Ord. III. Peridinaceae.
+
+**Coccospheres and Rhabdospheres (Murray, 13, 15)**
+
+In the surface waters of the ocean, especially in the Tropics, there have been found great numbers of exceedingly minute organisms to which the above names have been given. Our knowledge of their structure is due mainly to the investi-
+gations of Murray, who has described them in detail. They consist of a central pig-
+ment, and, imbedded in the cell-wall, calcareous plates of peculiar form. Fusion has been observed in some of them, but our knowledge of their life-history is still incomplete, and their affinities are very obscure.
+
+DIATOMACEAE (BACILLARIALES)
+
+The Diatoms are among the most widespread of plants, being exceedingly abundant in both fresh and salt water, or even upon the ground where it is damp. It is estimated that there are about ten thousand existing species, and they may occur in enormous masses, at times discoloring large bodies of water in which they are suspended. While any number great variety of form and size, the structure is essentially the same in all of them, and they constitute
+
+![]() A diagram showing a diatom with two chromatophores and the nucleus.
+![]() B A diagram showing a diatom with two valves.
+![]() C A diagram showing a diatom with two valves.
+![]() D A diagram showing a diatom with two valves.
+
+Fig. 60.—Diatomaceae. A, Navicula sp., showing the two chromatophores and the nucleus, × 1000; B, Cymbella sp., showing the two valves, × 1000; C, Cymbella imitans (× 500); D, Nitzschia signifera, showing the two valves (× 200).
+
+or
+
+CLASSIFICATION
+87
+
+a very natural group. They are unicellular organisms, but may be united into chains or filaments, or by the secretion of a gelatinous matter they remain together in colonies of characteristic form, adhering to each other by means of a gelatinous substance. These contain, besides chlorophyll, a golden-brown pigment, Diatomin. They are all characterised by the formation of a rigid silicious shell, which is composed of two pieces (valves), one of which fits into the other.
+
+Cell-structure of Diatoms. — While the form of the Diatoms is extremely varied, the commonest of the fresh-water forms are oblong, or somewhat boat-shaped in outline, e.g. Navicula (Fig. 60, A), Pinusaria (Fig. 60, B). The valves of these forms are in two parts, one fitting over the other like the cover of a pill-box. Each of these valves consists of two parts: the top, and the margin or girdle—corresponding respectively to the top (or bottom) of the box, and its side. The girdle is usually more or less separated between the top of the valve and the girdle. The finity shell is usually elaborately sculptured (Fig. 60, C), the markings often being excessively fine, and sometimes used as test for microscopic lenses. In the case of some forms, such as Navicula, there is a straight or curved line, with an enlargement at the middle and end of the valve. This line is known as the raphé, and has been shown to form a cleft or system of openings communicating with the interior of the cell.
+
+The cytoplasm in these elongated forms lines the cell-wall, and in the middle of the cell forms a bridge across it, in which lies the nucleus. In other forms the nucleus is suspended in the peripheral cytoplasm, or even suspended in the central vacuole by cytoplasmic threads running along the peripheral cytoplasm. Conspicuous oil-drops are often seen within the cell.
+
+Thermosiphons in Diatoms. — The thermosiphons of the Dia-
+toms are usually large plates, not commonly two lying parallel and touching each other throughout the whole length of the cell. Sometimes, e.g., Cocconeis,
+at a single one is present,
+which may be variously oval and of irregular form.
+Fig. 61.—Marina Diatoms. A, Leucodora sp. (× 200). B, Tetracoccus sp., three individuals connected by gelatinous joint. C, end view of a cell (× 200).
+
+![]() A
+![]() B
+![]() C
+
+88
+BOTANY
+
+Less commonly, e.g. Isthmia, the chromatophores are numerous small oval ones, like those common in the higher plants.
+
+The shape of the Diatom-cell is to some extent correlated with the habits of the different forms.
+
+The commoner fresh-water types, which live separately and form coatings on the surface at the bottom of the water, are commonly oblong or spindle-shaped. Those which are attached at one end, e.g. Nitzschia, Rhizosolenia, etc., are usually shorter, and often differently shaped at the free and attached ends. The floating forms, in which they are mixed with the plankton of the ocean (Fig. 62), have special contrivances for increasing their buoyancy. They are either lacunose or crenulate, e.g. Rhizosolenia; or have slender extensions of the cell, e.g. Chato-
+ceras, or they are thin discs, e.g. Cymbella, Plagiochila.
+
+**Movements.** The elongated Diatoms, which live free, often show active creeping movements, by the protrusion of protoplasmic processes through the openings along the raphae. By the contraction of these pseudopodia it is supposed that the cell is dragged along the surface to which it is applied.
+
+**Cell-division.** The cells divide in a plane parallel with the surface of the valves. The two new protoplasts separate when two valves open until only their edges are in contact. The nucleus then divides, and this is followed by a division of the protoplast into two, but without a cell-wall between them. The division of the nucleus takes place before that of the protoplasts. Each of the protoplasts now forms a new valve on its inner side, i.e. the side towards which it was originally placed. These new valves are placed back to back, and fit into the old valves, and thus the two new Diatoms are completely enclosed within the original pair of valves. As each Diatom has a larger valve of one of the new Diatoms, it follows that the latter are of unequal size, and that after each division one of the resulting cells is smaller than the other. When the divisions are repeated rapidly, this soon results in a great diminution in the size of part of the cell, and the same species may exhibit
+
+![]() A B C O
+
+Fig. 61.—Pelagic Diatoms. A, Chato-
+cerus borealis (x 150); B, C. Plank-
+tonica Sol.; B', from above; C, from
+the side; D, from below (see text).
+
+**Cell-division.** The cells divide in a plane parallel with the surface of the valves. The two new protoplasts separate when two valves open until only their edges are in contact. The nucleus then divides, and this is followed by a division of the protoplast into two, but without a cell-wall between them. The division of the nucleus takes place before that of the protoplasts. Each of the protoplasts now forms a new valve on its inner side, i.e. the side towards which it was originally placed. These new valves are placed back to back, and fit into the old valves, and thus the two new Diatoms are completely enclosed within the original pair of valves. As each Diatom has a larger valve of one of the new Diatoms, it follows that the latter are of unequal size, and that after each division one of the resulting cells is smaller than the other. When the divisions are repeated rapidly, this soon results in a great diminution in the size of part of the cell, and the same species may exhibit
+
+CLASSIFICATION 89
+
+great variation in this respect. After a minimum size is reached, however, the size is restored by the formation of a new valve.
+
+It has been recently discovered that in some marine Diatoms (Coe-
+nacodium) a new valve may be formed, by successive division of the protoplast, from the old valve-protoplast (Fig. 60 B), each of which then secretes a new pair of valves (Fig. 61 A). As the valves in these small individu-
+als are very slightly silicified, it is not possible to see how they are able to increase in size, unlike the strongly silicified valves of most Dia-
+toms. In the case of the Coenacodium, by repeated divisions of the protoplast, a new valve is formed every year, just as much like this as in some of the simpler Peridiniae, e.g. Pyrocystis.
+
+Anaplasia means that the formation of auxospores may be either non-sexual or sexual. The simplest case, such as that of the genus *Euplotes*, shows no sex in the separation of the valves, so that the protoplast is not sexually increased in size, usually developing a continuous membrane about its periphery. But first one valve forms a single valve, like one of the original ones, and soon after a second one fitting into it, thus forming a new Diatom of the maximum size of the species.
+
+![Fig. 60 — A, B, auxospore formation in Cocconeis placentula. (After KARSTEN.) C, auxospore formation in Euplitesia sp. (After FRYER.) In Cocconeis a single spore is formed from the cell of the undivided protoplast. In Euplitesia the proto-
+plast divides into two parts, each of which engulfs with its corresponding one
+of the other conjugating cell.)
+
+In other cases, e.g. Cocconeis (Fig. 64), the naked protoplast escapes from two cells, which are generally enclosed in a gelatinous envelope, and the two fuse
+
+![]() A: A cross-section of a diatom showing internal cell-division.
+![]() B: A cross-section of a diatom showing internal cell-division.
+![]() C: A cross-section of a diatom showing internal cell-division.
+
+90
+BOTANY
+
+into one; i.e. there is a true fertilization. From the cell thus formed a new Diatom is either formed at once or after a preliminary division of the proplast.
+
+Affinities of Diatomaceae
+
+The Diatoms are not, apparently, closely related to any other group of plants. In their cell-structure they approach the Desmidiæ, one of the lower orders of Green Algae, and in the structure of their shell, and their color, they may show some relation to the Peridiniæ. With the true Brown Algae they have little in common but their color.
+
+Fossil Diatoms
+
+The silicious shells of Diatoms are very resistant, and have been preserved, often in enormous quantities, in a fossil condition. It is remarkable, however, that they are quite unknown from the older formations, and it seems probable that the group as it now exists is of comparatively recent origin.
+
+Classification of Diatomaceae
+
+The Diatoms have been divided into seventeen families grouped under two orders. (Schütz, 18.)
+
+Ord. I. Centricia. Valves usually circular or oval in transverse sections. No raphe.
+
+Ord. II. Frustulata. The valves bilaterally symmetrical, markings usually pinnately arranged. Raphe usually present. Valves boat-shaped or rod-shaped in most of them.
+
+BIBLIOGRAPHY
+
+87. 1. De Bary, A., Fungi, Mycotocae, and Bacillariae. Oxford, 1867.
+80. 2. Beuchat, W., Untersuchungen über die Nische des Kieselsäure-Pringsheim. Jahrb. für wissenschaftliche Botanik, xxxv, 1000.
+97. 3. Davis, B.M., The Vegetation of the Hot Springs of Yellowstone Park. U.S.A., V.L., 1895.
+97. 4. Fischer, A., Vorleunungen über Diatomeen. Jena, 1897.
+87. 5. Gabelt, K., Originis de Chaetoceros, etc. Oxford, 1867.
+90. 6. Gaudry, J., Les Algues Chariotières, 1890.
+96–1900. 7. Karsten, G., Papers on the Reproduction of Diatoms. Flora, '96,
+'97, '98.
+98. 8. Kirchner, O., Schizophyceae—In Engler and Prantl, Die nattirlichen Pflanzenfamilien. Leipzig, 1896.
+94. 9. Liebig, E., Handbuch der Mycotocae. London, 1894.
+90. 10. Macbride, T.H., The Myxomycetes of North America. London and New York, 1900.
+91. 11. Miersch, W., Polycomyces. Engler and Prantl, Nat.Pflanzenfa-
+milien. Leipzig, 1896.
+
+![]() A diagram showing the structure of a diatom.
+
+CLASSIFICATION 91
+
+*90.* 12. Migulin, W. System der Bacterien. Jena, 1897-1900.
+
+*90.* 13. Murray, G. Introduction to the Study of Seaweeda. London and Edinburgh, 1897.
+
+*90.* 14. Murray, G. On the Reproduction of Some Marine Diatoms. Proc. Roy. Soc., 1898.
+
+*98.* 15. Murray, G., and Blackman, V. H. The Nature of Coccospheres and Rhabdospheres. Phil. Trans. Royal Society, Vol. 190, 1898.
+
+*90.* 16. Murray, G. The Structure and Reproduction of the Diatoms of the Atlantic. Trans. Linnean Soc., Vol. V, pt. 1, 1898.
+
+*97.* 17. Schröter, J. Myxocytozoen. Engler and Prantl, Nat. Phasmenf.
+
+*96.* 18. Schütz, F. Peridinalese, Bacillariaceae. Engler and Prantl, Nat. Phasmenf., Leipzig, 1896.
+
+*00.* 19. Seidel, E. Flora von Bayern und Prusia, Nat. Phasmenf., Leipzig, 1900.
+
+*97.* 20. Süssmayer, F. Das Botanische Practicum. Jena, 1897.
+
+*92.* 21. Thaxter, R. On the Myxobacteriaceae, a new order of Schizomycetes.
+Bot. Gazette, XVII, 1892.
+
+*97.* 22. ——— Further observations in the Myxobacteriaceae. Bid., XXIII,
+1897.
+
+*97.* 23. Tubbsel, K. Diseases of Plauna. London and New York, 1897.
+
+*97.* 24. White, F Fresh-water Algae of North America Bethlehem, Pa.,
+
+CHAPTER V
+
+THE ALGE
+Thallophytes
+
+All plants below the Mosses are often placed in a single sub-
+kingdom Thallophyta, but there are good reasons for considering
+the two great divisions above mentioned, the Mosses and below the Mosses,
+as entitled to the rank of subkingdoms. Those forms which possess
+chromatophores are known as Algae; those from which they are
+absent, Fungi. The Schizophytes are often included with the Alge,
+but they, with the Pteridophytes, are known as Flagellata, which are
+sometimes united with the lower Alge under the name Protophyta,
+are probably also better regarded as subkingdoms.
+
+The Alge
+
+The Peridinidae and Diatomacea, both of which groups are related
+more or less closely to the higher Alge, may probably best be con-
+sidered as separate classes. In order to facilitate their classification among these aside, the Alge are usually divided into three classes, the
+Green Alge (Chlorophyceae), the Brown Alge (Phaeophyceae), and
+the Red Alge (Rhodophyceae). The supplementary pigments which distinguish these three classes from each other are associ-
+ated with marked structural differences which sharply differentiate the three classes. One group of the Green Alge, the Characea, may
+perhaps be better removed from that group and considered as a
+fourth class.
+
+CLASS I. THE GREEN ALGE (CHLOROPHYCEAE)
+
+The Green Alge are especially interesting because, with little
+question, they represent more nearly than any other existing plants
+the ancestors of the green land-plants. The Phaeophyceae and Rho-
+dophyceae have been supposed to be derived from them by more
+specialized forms, especially adapted to a marine environment, and
+as having diverged widely from the forms which have given rise
+to the higher green plants.
+
+Chromatophores. The Chlorophyceae always contain distinct chro-
+matophores, which seldom show any other color than pure green,
+
+92
+
+THE ALGA 98
+
+although occasionally a red pigment (Haematochrome) is present.
+Such forms, however, may usually have pure green chromatophores as well.
+
+Nucleus. — A nucleus is always present in the cell, and there may be more than one.
+
+The greatest number of Green Algae are fresh-water organisms, or may grow upon damp earth, trunks of trees, or other places where a sufficient amount of water is present for their needs. Some of them are marine, and others grow associated with other plants.
+Thus the so-called "galls" of many Lichens, are Green Algae,
+which may grow quite independently of the plant to which they occur within the tissues of the higher plants. *Chlorochetrium Lemae* is a unicellular green Alga which lives within the intercellular spaces of the leaves of *Lemna*, and is known as *Trichodina*.
+
+Plant-body. — The simplest of the Chlorophyceae are unicellular, but they are more commonly cell-rowa, either simple or branching. A smaller number (e.g. *Ula, Colchecete*) have a flat thallus. They show no external differentiation, this being most marked in the Stoneworts, *Chlorella*, which also contain the largest members of the class.
+
+Reproduction. — In spite of the simple vegetative structure, there is a good deal of variation shown in their reproductive processes. Cell-division occurs much as in the higher plants. Where the cells are multinucleate, division-walls may be formed without a corresponding nuclear division, but in the uninucleate cells, the nucleus undergoes mitosis as in all cells of the higher plants. In unicellular forms, of course, each cell-divides results in the formation of new individuals.
+
+In most forms special sexual reproductive bodies are developed.
+The sexual cells these are naked, united cells (Zoospores, Swamps), which are formed either singly, or several together, from the mother-cell, and after a longer or shorter period of activity, settle down and form a new plant. Where these cells are destitute of chlorophyll and cannot live within the plant body they are known as "Aplasmonopore". Less frequently, as in the buds of some of those Characeae, these reproductive bodies are multicellular.
+
+Sexual Reproduction. — Most Chlorophyseae show a clearly marked sexual reproduction. The sex-cells in lowest forms are not distinguishable from the vegetative ones. In more highly differentiated forms like the Desmids, the protoplasts of two ordinary individuals unite to form the sexual spore. More commonly, however, special sexual cells are generated by budding. These may be entirely similar (Planktonic), or they may be more or less perfectly differen-
+tiated into male and female cells. The product of the united gametes is known as the Zygotc, and usually becomes a thick-walled
+
+94
+BOTANY
+
+spores, which germinate only after a considerable period of rest.
+Much less commonly (e.g. Ulva), the zygote germinates immediately.
+The simpler forms of gametes closely resemble the non-sexual zoospores, from which they have undoubtedly developed. Occa-
+sionally gametes, male as well as female, have been observed to
+germinate without fertilization. This phenomenon is known as
+Parthenogenesis.
+
+Certain groups of Green Algae, e.g. Volvoxaceae, still exhibit all
+grades of development of the gametes, from non-sexual zoospores to
+perfectly formed gametes. The latter, however, usually lose the power of movement, and remain within the mother-cell
+(Ogonium), where they are fertilized by the small active spermatoid.
+
+![]() A: A colony of Gonium pectorale (× 400); B: a single cell of Gonium (× 800); c, chloroplast; d, nucleus; e, eye-spot.
+
+![]() C: Pediastrum californicum (× 50); the arrow indicates the forward pole of the colony. D, three stages in the division of a gametid. (D, after Sow.)
+
+Classification of Chlorophyceae
+
+The Chlorophyceae may be divided into the following six orders:
+I. Volvoxaceae ; II. Protoecioides ; III. Confoecoides ; IV. Con-
+jugatae ; V. Siphonae ; VI. Characeae. Of these, the first three
+
+THE ALGAE
+
+86
+
+are unquestionably closely related, and probably lead up to the higher green plants. The others are more specialized forms, probably de-
+rived from the Chlorophyceae, but differing in some of their obvious relationships. The Conjugatae are sometimes removed from the Chlo-
+rophyceae, but this seems hardly warranted. As stated before, the
+Characeae differ much from the other forms, and might with propriety
+be considered as a class, coordinate with all the other Chlorophyceae.
+
+Order I. Volvocacean
+
+The Volvocaceae are at once distinguished from the other Green
+Algae by the fact that their vegetative cells are ellipsoid, and the
+plants are therefore actively motile. They may be either unicellu-
+lar, or they are cell-families more or less intimately united. In the
+former case the cells are usually spherical or ovoid, and possess proplasmic
+threads, and the whole should be considered as a single multicellular
+organism, and not a colony of unicellular individuals.
+
+The cells of most Volvocaceae resemble closely the zoospores of
+many of the higher Chlorophyceae. They are oval or globular in
+form, surrounded by a membrane which may be of unmodified celu-
+lose, but is more often more or less gelatinous and very thick (Fig. 65,
+A, B). This membrane or envelope is perforated by minute flagel-
+la to protrude. There is usually a single large chromatophore present.
+This is somewhat cup-shaped, and in most cases its base is in the
+chromatophore is a large roundish body, the pyrenoid, a structure fre-
+quently found in the chromatophores of the higher plants, though
+still somewhat obscure. The pyre-
+noid is of aluminous nature, and is probably associated with the assimil-
+ation of carbon dioxide.
+
+The pyrenoids are sometimes re-
+garded as similar to the protein-
+crystals, found as reserve-food in the
+cells of many plants. They occur in
+the cytoplasm within the cavity of
+the cup-shaped chromato-
+phore, and in the cytoplasm near
+the base of the two long cells, usu-
+ally two small contractile
+vacuoles. There is also present at the forward end a red pigment.
+
+Fig. 65.--Schematic stages in the division of an individual Volvox.
+(Confusius, seen from above at left; from below at right.) A, B, C, D, E, F, G, H, J, K, L, M, N, O, P, Q, R, S, T, U,
+V, W, X, Y, Z. A', B', C', D', E', F', G', H', J', K', L', M', N', O', P', Q', R', S', T', U', V', W', X', Y', Z'. The same
+stages on the following day.
+After Sauvage.
+
+![]() A schematic diagram showing the division of an individual Volvox.
+![]() A close-up view of a Volvox cell showing its structure.
+![]() A close-up view of a Volvox cell showing its structure.
+![]() A close-up view of a Volvox cell showing its structure.
+![]() A close-up view of a Volvox cell showing its structure.
+![]() A close-up view of a Volvox cell showing its structure.
+![]() A close-up view of a Volvox cell showing its structure.
+![]() A close-up view of a Volvox cell showing its structure.
+![]() A close-up view of a Volvox cell showing its structure.
+![]() A close-up view of a Volvox cell showing its structure.
+![]() A close-up view of a Volvox cell showing its structure.
+![]() A close-up view of a Volvox cell showing its structure.
+![]() A close-up view of a Volvox cell showing its structure.
+![]() A close-up view of a Volvox cell showing its structure.
+![]() A close-up view of a Volvox cell showing its structure.
+![]() A close-up view of a Volvox cell showing its structure.
+![]() A close-up view of a Volvox cell showing its structure.
+![]() A close-up view of a Volvox cell showing its structure.
+![]() A close-up view of a Volvox cell showing its structure.
+![]() A close-up view of a Volvox cell showing its structure.
+![]() A close-up view of a Volvox cell showing its structure.
+![]() A close-up view of a Volvox cell showing its structure.
+
+96
+BOTANY
+
+spot (eye-spot), like that found in some Flagellata. Occasionally (e.g. Chlorogonium) there may be two flagella, ciliates, and in the genus Chlorotricha there are five cilia.
+
+**Movements—The Volvox** are actively motile, and the movements are strongly influenced by light. The eye-spot is with little quantity con- nected with this sensi- tiveness to light. In the movement of the cells about the forward pole of the globular cell- family have the eye-spot more or less developed than the cells at the hinder pole.
+
+Fig. 87.—A, *Sphaeridia phaeota*, active individual (*× 300*). B, *Chlamydomonas* (*× 500*). C, cells of *Volvox minor*, showing protoplasmic connections, and a young anthidium, *5* (*× 500*). D, *Volvox* (*× 500*), showing the large central nucleus, and the peripheral flagella. E, *Sphaeridia* (*× 300*). F, a spermatoid (*× 300*). G, *Chlamydomonas* (*× 500*). H, *Chlamydomonas* (*× 500*).
+
+Classification of Volvoxaceae
+
+The Volvoxaceae may be divided into three families: Chlamydomonadaceae, Phaeotomaceae, and Volvoxaceae. The first two comprise unicellular forms, the latter are all multicellular.
+
+**Chlamydomonadaceae—In the Chlamydomonadaceae the uncellular free-swim- ming cells may withdraw their cilia and assume a non-motile condition in which they are capable of repeated fusion, giving rise to large colonies of non-motile cells which are able to move only by means of their flagella. This condition is very closely distinguishable. Sphaeridia nivalis, the "Red-moss" plant, is an example of this. In this plant, as well as in the spores of other Volvoxaceae, the red pig- ment becomes visible when the cells become non-motile. The cells then separate from their granular matrix and resume their active form. Gametes are formed by internal division of each cell, these being either quite similar or equally dif- ferent in size. The gametes fuse together and the resulting zygotes contain cells finally divide into several (2–4) parts, each of which escapes as a free-swimming cell.
+
+**Phaeotomaceae—The Phaeotomaceae include a small number of unicellular forms**
+
+![]() A diagram showing a cross-section of a Volvox cell.
+
+![]() A diagram showing a cross-section of a Volvox cell.
+
+![]() A diagram showing a cross-section of a Volvox cell.
+
+![]() A diagram showing a cross-section of a Volvox cell.
+
+![]() A diagram showing a cross-section of a Volvox cell.
+
+![]() A diagram showing a cross-section of a Volvox cell.
+
+![]() A diagram showing a cross-section of a Volvox cell.
+
+THE A.L.G.E.
+97
+
+(Phacotus, Pteromonas, etc.), distinguished by having the cell-membrane firm,
+and often composed of two parts.
+
+The Gymnodinaceae, including Volvoxacum belong to the third family. These are always multicellular. The simpler forms (Gonium, Pandorina) consist of a single cell, which is divided into two by repeated bipartition of this cell. New cell-families arise which are free by the softening of the gelatinous matrix of the mother-cell. In the genus Pandorina the cells are very large, and are incapable of division, and much larger ones (gonidia) which by division give rise to the new plants. In Pandorina the gonidia are circular, and except in the smallest species, they are surrounded by a gelatinous sheath. The gonidia is small (rarely over 10-12), and they are many times larger than the other cells, which may be several thousand in number. The multiplication of the Vol-
+voxacum is effected by means of a special kind of cell called a protoplast. This is colored green by the multitude of these swimming colonies.
+
+In Pandorina the protoplasts are connected with each other by a condensate seen results in the formation of a hollow sphere in which the cells are first in contact, but separate more and more with the development of the mucilaginous cell-walls. The latter penetrate into the gelatinous envelope of the female plant, where they come in contact with the egg-cells and effect their fertilization. In Volvoxacum the protoplasts are connected with each other by a network of vacuoles, are quite destitute of cilia, and very much larger than the spermato-
+nids, which are largely composed of nuclear substance.
+
+It is also interesting that in Gonium and Pandorina there is very little difference between the sexual and non-sexual cells, and the gametes are alike (Fig. 67, B). In the genus Endorina certain cells assume the function of eggs, while others undergo changes similar to those described for Gonium and Pandorina. The latter penetrate into the gelatinous envelope of the female plant, where they come in contact with the egg-cells and effect their fertilization. In Volvoxacum there is no such communication between the sexual and non-sexual cells, but there is a gradual evolution of the sexual cells.
+
+Affinities of Volvoxacum:
+
+The Volvoxacum are probably directly related to the Flagellatae, and through these show affinity with the lower animal forms. Indeed, they are actually claimed by some zoologists as animals. Their very evident relationship with the Protozoococcideae, and through these with the higher plants, however, indicates that although they cannot be regarded as true plants in any absolute sense, they at least respect true plants, and probably represent the starting-point for the line of development leading up to the higher green plants. It is however, among the simpler forms, like Chlamydomonas, that we see to look for the connection with the Protozoococcideae, and not among highly specialized forms as Volvox.
+
+![]() A diagram showing a Volvox aculeate colony.
+TOPIC
+
+96
+BOTANY
+
+**Order II. Protococcoidae**
+
+The Protococcoidae are unicellular plants distinguished from the Volvocaceae by the absence of cilia in the vegetative cells. The cells may be isolated, or may be united into colonies or cell-families, often of characteristic form and large size. Many of them produce motile reproductive cells, which are sometimes not distinguishable from such Volvocaceae as Chlamydomonae. As the latter often multi- pply for a long time in a non-motile condition, it is sometimes impossible to be sure whether a given organism belongs to the Proto- coccoideae or Volvocaceae. It is extremely probable that the lower Protococcoidae are derived from simpler Volvocaceae, by the permanent loss of motility in the vegetative cells - a character common to all plants above the Volvocaceae.
+
+The Protococcoidae are mainly fresh-water plants, growing either completely submerged, or simply in fresh water, on shaded earth, trunks of trees, or rocks. Some of these grow associated with other organisms. The green color of certain organisms — fresh-water
+
+![]() A small circular image showing a single cell.
+![]() B A larger circular image showing multiple cells in a colony-like arrangement.
+![]() C A smaller circular image showing a single cell with a central nucleus.
+![]() D A larger circular image showing multiple cells in a colony-like arrangement.
+![]() E A smaller circular image showing a single cell with a central nucleus.
+![]() F A larger circular image showing multiple cells in a colony-like arrangement.
+![]() G A smaller circular image showing a single cell with a central nucleus.
+![]() H A larger circular image showing multiple cells in a colony-like arrangement.
+
+Fig. 86. — A. *Fleurococcus vulgatus*. I, full-grown individual; II, III, cells dividing.
+B. *Apisocystis Brunsvicensis*. Young colony attached to a filament of *Oedogonium* (p. 380).
+C. *Chlamydomonas nivalis*. One of the cells has divided to form a young colony.
+D. *E. S. dimophasus*. Full-grown colony; E, young colony still enclosed in the membrane of the mother-cell.
+F. *Pseudocystis*. One of the cells dividing; G, young colony still enclosed in the membrane of the mother-cell.
+H. *Pseudocystis*. Young colony; H, young colony still enclosed in the membrane of the mother-cell.
+
+All figures except B, x about 500.
+
+THE ALGAE
+
+90
+
+sponges, Hydra, and some Infusoria—is due to the presence of minute Protococcoides. Other forms grow within the intercellu-
+lar spaces of various aquatic Flowering Plants, while the gonidia of many Lichens are identical with certain species of Protococcoides.
+
+Of the simpler Protococcoides, one of the commonest is *Phaeococcus vulpirtus* (Fig. 68), which is found in the leaves of many plants and similar objects. The individual plant is a small globular cell with definite cell-membrane, several chromatophores, and a centrally placed nucleus. The cells multiply by fission, but no sexual cells (gametes) are known. Other forms, e.g. Chlorophyta, give rise to swarm-spores closely resembling the simpler Volvoxaceae, while a few of them, e.g. *Tetraspora*, have also simple sexual cells. The cells in *Trirapsis*
+
+![]() A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
+**Fig. 68.—Hydrodictyon utriculatum. A, protoplasm of a cell dividing into zoospores. B, two free zoospores. C, zoospore uniting to form the young net. D, a somatic cell dividing into two daughter-cells. E, zoospore dividing into two daughter-cells. F, the single equatorial chromatophore with a single pyramidal and a single nucleolus. G, zoospore dividing into four daughter-cells (*x 300). H, (*x 300); I, (*x 300); the others, *x about 500.* F, after Klauer.)
+
+and *Acylocystis* (Fig. 68, B) are imbedded in a gelatinous matrix, in which probably these forms are held together.
+
+*Hydrodictyum.*—The most specialized of the Protococcoides, which con-
+tain cells with nuclei and chloroplasts, are represented by the com-
+mon green alga *Hydrodictyum*. In this genus the nuclear division takes place, except when new families are to be formed. The simplest of those (sometimes placed in the Phaeococcoides) are represented by the com-
+mon green alga *Hydrodictyum*. In this genus the nuclear division takes place,
+eight spindle-shaped cells, sometimes with long appendages growing from the end cells. In reproduction, each cell divides into two to eight daughter-
+cells, which then become vegetative in the form of the mature plant. No
+other form of reproduction is known.
+
+*Hydrodictyum.*—*Hydrodictyum*, the Water-spear (Fig. 68), is the representative of the family Hydrodictyaceae. The plant is a gelatinous net, sometimes ten centimetres or more in length. The individual cells of which it is composed finally may reach a length of several millimeters. The cells are
+
+100
+BOTANY
+
+oblong, thick-walled, and the cytoplasm forms a thick layer next the wall, leaving a large central sap-cavity. Imbedded in the cytoplasm are numerous nuclei and a few chloroplasts. The cell then divides by a longitudinal fissure in the thin plate, which finally becomes separated into many small chromatophores.
+
+Reproduction.—When the cells have reached a certain size, the protoplastic contents are drawn off from the cell-wall, and the cell-divides into two daughter-cells, each of which has a nucleus and a small piece of the chromatophore. These cells then separate from one another, and each of them divides again about one short time within the mother-cell, where they soon come to rest, having arranged themselves end to end, so as to enclose small polygonal areas (Fig. 66, A), which are surrounded by a thin membrane, and thus form the mother-cell in a mould. The wall of the mother-cell slowly adheres and dis- solves, as the young net grows, and finally it is set free in the water; and finally grows to a certain size, when it also divides into two daughter-cells. In this young net (Fig. 66, E) each cell has a single nucleus and a circle-shaped chromatophore containing a single pyrondine. As the cells grow, the nucleus divides repeatedly, and the pyrondines increase in number until they become numerous, and often presenting a somewhat reticulate appearance. Numerous pyrondines also arise in the young net.
+
+Sexual reproduction.—The sexual reproduction consists in the division of the contents of certain cells into a very large number (sometimes 30,000) of motile cells (Fig. 66, B). These cells then separate from one another, and the mother-cell unites in pairs (Fig. 66, C) to form the zygote, which, after increasing in size, gives rise later to several large swarm-spores, which in turn produce smaller swarm-spores. The swarm-spores are formed in groups; and individual spores are formed small nets, such as in the ordinary cells.
+
+It has been observed that when the plants are grown in salt solutions (e.g. a two per cent solution of malose), the tendency to form new nets is increased; but when they are grown in a solution of cane sugar, the production of gametes is greatly diminished.
+
+The beautiful star-shaped colonies of Pedicularia (Fig. 66, P) are similar to at least some of those of Pseudococcum. In contrast with these is that of Hydractyloa, the main difference being that the swarm-spores escape from the mother-cell, enclosed in a delicate membrane, within which they arrange them- selves in the form of the colony.
+
+Affinities of Protococcoides
+
+The simpler Protococcoides are closely related on the one hand to the simpler Volvoxaceae, on the other to the lower members of the Coniferaceae. The former group includes species belonging to nearly the genus Ulva, and many of the unicellular forms like Chlorococco- cum are extremely like the early stages of many of the filamentous Coniferaceae.
+
+The Protococcoides (Engler and Prantl, 9) may be divided as follows:
+
+a. Vegetative cell-division present.
+1. Zoospores present. Families: Tetrasporaceae, Chlorospha- racae.
+2. Zoospores absent. Family: Piroccoccaceae.
+
+![]() M85U
+
+THE ALGAE
+101
+
+b. No vegetative cell-division.
+1. Unicellular forma. Family : Protoocaceae.
+2. Multicellular colonies of definite form. Family : Hydrodictyaceae.
+
+Order III. Confervoidae
+
+The Confervoidae, in their fully developed form, are always truly multicellular, although they not infrequently may vegetate for a long time in a unicellular condition (Palustic stage), which is hardly distinguishable from certain Proto- cocci. This has given rise to a good deal of confusio-n in their classi- fication. While they are mostly
+
+Fig. 35.--Cells from the thallus of the Jatrea (x 300).
+
+fresh-water plants, some of them, like the Slime-mosses (Ulva), and species of Cladophora and Chatophora, are characteristic marine. Others grow in moist air, attached to trees and other objects by means of such, for instance, are the genera Tren- tepohila, Mycenden, and others. Still more remarkable is the curious genus Trichophila, which grows among the hairs of the Sloth (Bradypus). Mycenden is a true parasite upon the leaves of various plants.
+
+Fig. 36.--A, Siphonochlamys tener (x 100). B, a single cell (x 800), showing the single chromatophore, a nu- cleus, C, Microspora sp. (x 300). D, Drapetisella sp. (x 300). E, Thalassia sp. (x 300). F, a nucleus. F', conjugating gametes of Ulvastrum zonato. (P., after Dumont.)
+
+![]() A diagram showing a single cell with a nucleus and chromatophore.
+![]() B A single cell (x 800), showing the single chromatophore, a nucleus.
+![]() C A microspore (x 300).
+![]() D A drapetisella sp. (x 300).
+![]() E Thalassia sp. (x 300).
+![]() F A nucleus.
+![]() F' Conjugating gametes of Ulvastrum zonato.
+
+102
+BOTANY
+
+The Plant-body. — The Confervoidae show considerable range of structure. The simplest forms (e.g. Conferva, Microspora, Fig. 74, C) are unbranched cell-rows, the cells entirely similar. In other forms, e.g. Cladophora, the plant-body is branched, the branches connected to base and apex, the former attached by a special root or disk. Branching filaments, e.g. Cladophora, Chetophora, are common, and sometimes, as in Dnarnapalida (Fig. 71, D), the smaller branches contain most of the chlorophyll and constitute very simple assimilative structures. Less commonly, as in Ulva and Codonodendron (Fig. 77), the plant-body has the form of a thallus.
+
+Cell-structure. — The cells usually have the protoplasm confined to the periphery of the single large cell-sphere, but sometimes there are bands traversing this and dividing it into more or less complete chambers (Cladophora). A single nucleus, imbedded in the peripheral cytoplasm, is found in most cases, but occasionally (Clado-phaea, Sphaerocystis) the cells may be uninucleate. There may be a single large chromatophore, usually containing a single pyre- noid, or there are numerous chromatophores distributed through the cytoplasm. The cell-wall may be thin and homogeneous, or it may show more or less evident striation (Cladophora). The plants are sometimes covered with a gelatinous matrix, such as is found in the common genus Chetophora.
+
+Cell-division. — In multicellular cells like those of the common genus Cladophora, division-walls are formed between any pair of adjacent nuclear divisions; in this case the wall begins to form as a delicate circular ridge of cellu- lar protoplasm projecting into the cell-lumen. This ridge grows toward the centre of the cell, and finally forms a circular division-wall which cuts the plant-body in two.
+
+Where a single nucleus is present, this divides in two during each nuclear division; a divi- sion-wall is formed. The latter may form gradually, as in Cla- dophora, or it may be formed simultaneously with the nuclear division. The mode of ordinary cell-division is seen in the com- mon genus Eudogonium (Fig. 72). Here, before the nucleus divides, there is formed near
+
+![]() A diagram showing a cross-section of a plant-body with a single nucleus and a division-wall forming between two nuclei.
+
+Fig. 72.—A (Eudogonium autotomum) shows
+a cell in process of division; r., r., the
+cellulose ring, which stretches to form
+the new cell-wall; o., o., represents
+the same cell 15 minutes later;
+o., o., the same cell 30 min.
+
+
+THE ALGAE
+103
+
+the top of the cell, a thick cellulose ring which is attached to the inner surface of the cell-membrane. The division of the nucleus follows between this ring and the outer membrane of the cell. The latter is not attached to the outer membrane of the cell, but is quite free at the margin, and can therefore shift its position. The cellulose ring at the top of the cell splits circularly, and is rapidly drawn out into a tube which passes through the length of the cell. This division-wall is pushed up until it occupies the centre of the divided cell, and then grows to the outer wall, completing the division into two cells. Of these cells, the lower has its lateral walls composed of original cell-wall, while that upper has its walls thickened by derived mainly from the cytoplasm formed from the cellulose ring. The small piece of the old wall above the ring is evident as a little cap surrounding the upper end of the cell. This process is repeated with each division, and thus the cells of Zospe- mum show a series of these little caps, indicating the number of times the cell has divided.
+
+Reproduction. -- Most of the filamentous Confoederata may form new individuals by the separation of portions of the plant-body, or even by the separation of the individual cells in some cases. Most commonly, however, special reproductive cells are produced.
+
+Zospeum. -- The commonest forms of non-sexual cells are zoospores, or swarm-spores, produced either singly, by the escape of the whole protoplast, or in doublets (Fig. 73). After a preliminary division of the protoplast into two parts (Fig. 74), one of these swarm-spores may escape through a pore in the mother-cell, or the filament may break, so as to open the end of the cell (Fig. 73). The escape of the swarm-spore from the mother-cell is probably aided by the swelling of mucilage developed within the mothercell.
+
+The free-swarm-spore has usually an oval form, with two or four cilia (Fig. 71, E). Less frequently there is but a single cillum (Con-
+
+![]() A
+![]() B
+![]() C
+![]() D
+
+Fig. 73.--A, cell of Zospeumum ep., with a zoospore escaping through a pore in its side; B, free zoospore (x 500); C, free zoospore (x 500); D, formation of zoospores in germinating Zospeumum ep., after Paracoccus.
+
+4
+
+104
+BOTANY
+
+ferae), or a crown of numerous cilia (Eldogonium). There is generally an eye-spot like that in the cells of the Volvoxaceae, and there may be a second one, but these are not conspicuous, so that the resemblance to the simpler Volvoxaceae is very striking. After a brief period of activity, during which the cell elongates markedly and is sensitive to light, they come to rest, and secrete a thin cellulose membrane. The ciliated end becomes attached, and soon develops into a disc-like roo-lim organs which attach it to the substratum. The cell elongates, and, dividing repeatedly, develops quickly into the characteristic form.
+
+In certain forms (e.g. Stigeonionum) the plant often remain for a long time in a unicellular condition, the cells being produced when they divide, thus producing a large number of small multicellular plants, which are scarcely distinguishable from many Protozooidae. Sooner or later, these cells develop into the filamentous form of the mature Alga.
+
+Aplanopores --- Less commonly the non-sexual reproduction is due to the formation of Aplanopores; i.e. the cell-contents contract, and develop a new wall within the mother-cell, thus forming zoospores, or later developing into plants. These are called the so-called "Akinetes", which differ from the Aplanopores only in having the cell-wall derived from the wall of the mother-cell.
+
+Sexual Reproduction --- In all the higher types of Volvoxaceae has yet been demonstrated for all the Confoerideae it is probable that it always occurs. This is seen in its simplest form in Ulva and Ulothrix (Fig. 71, F). The gametes in these forms are quite similar (Ulva), or there may be a slight difference in size and shape between them. In some species there may be two or four gametes instead of one. The zygote resulting from their conjugation may either germinate at once (Ulva) or it may become a resting-spore, from which are developed swarm-spores.
+
+In all of these higher types, the differentiation of the sexual cells is well marked, and the egg-cell is quite distinct from the sperm-cell. The cells containing the gametes are generally spherical or oval-shaped. This is shown in Fig. 73 (Fig. 75), where the oogonium, the cell containing the egg-cell, is a good deal enlarged, while the antheridium, containing the male cells (spermatozoids), is much smaller than the vegetative cells. In the peculiar genus Spirogyrae, whose cells
+
+![]() A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
+
+Fig. 74.--Germinating zoospores of Eldogonium sp., f., holotypus (p. 300).
+
+**Notes on Volvox**
+
+The Volvox are simple colonial organisms consisting of a single cell with a large central vacuole and several rows of cilia around its periphery. They are found in fresh water lakes and ponds throughout Europe and America. The cells are usually spherical in shape, but sometimes they assume other forms such as ellipsoidal or cylindrical. The cilia are arranged in rows around the periphery of each cell, and these rows are known as "rings". Each ring consists of three to five rows of cilia, and these rows are separated by narrow spaces. The cilia are used for locomotion and also for feeding purposes. The food particles are taken up through the mouth and then passed along a tube-like structure called the "food canal" to the digestive vacuole where they are broken down and absorbed by the cell.
+
+The Volvox have a unique method of reproduction known as "vegetative reproduction". This involves the division of individual cells into two or more daughter cells which then grow outwards to form new colonies. This process can occur either by budding off from existing colonies or by splitting off from individual cells.
+
+The Volvox also have a method of reproduction known as "spore reproduction". This involves the formation of spores which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "gamete reproduction". This involves the formation of gametes which can then fuse together to form new colonies.
+
+The Volvox have a unique method of reproduction known as "resting-sporulation". This involves the formation of resting-spores which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "swarm-spore production". This involves the formation of swarm-spores which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "zygote formation". This involves the formation of zygotes which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "resting-sporulation". This involves the formation of resting-spores which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "swarm-spore production". This involves the formation of swarm-spores which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "zygote formation". This involves the formation of zygotes which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "resting-sporulation". This involves the formation of resting-spores which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "swarm-spore production". This involves the formation of swarm-spores which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "zygote formation". This involves the formation of zygotes which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "resting-sporulation". This involves the formation of resting-spores which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "swarm-spore production". This involves the formation of swarm-spores which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "zygote formation". This involves the formation of zygotes which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "resting-sporulation". This involves the formation of resting-spores which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "swarm-spore production". This involves the formation of swarm-spores which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "zygote formation". This involves the formation of zygotes which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "resting-sporulation". This involves the formation of resting-spores which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "swarm-spore production". This involves the formation of swarm-spores which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "zygote formation". This involves the formation of zygotes which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "resting-sporulation". This involves the formation of resting-spores which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "swarm-spore production". This involves the formation of swarm-spores which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "zygote formation". This involves the formation of zygotes which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "resting-sporulation". This involves the formation of resting-spores which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "swarm-spore production". This involves the formation of swarm-spores which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "zygote formation". This involves the formation of zygotes which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "resting-sporulation". This involves the formation of resting-spores which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "swarm-spore production". This involves the formation of swarm-spores which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "zygote formation". This involves the formation of zygotes which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "resting-sporulation". This involves the formation of resting-spores which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "swarm-spore production". This involves the formation of swarm-spores which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "zygote formation". This involves the formation of zygotes which can then germinate to form new colonies.
+
+The Volvox have a unique method of reproduction known as "resting-sporulation". This involves the formation
+
+THE ALOE 106
+
+are multinucleate, the ordinary cells may be transformed, without change of form, into ologonia or amheridia, the former containing several egg-cells, the latter many spermatozoa.
+
+The odgonium in Odogonium is usually the upper of the two cells formed from division of one of the outer cells, so that several of the characteristic corks are usually found in the same cell. In the process of division, at the time of the division, the cellulose ring stretches out quickly, swelling out at the same time, so that the two cells are separated by a narrow space between the nuclei. Sometimes the lower of the two cells also becomes an odgonium. The odgonium of Odogonium, but later they contract, becoming denser, alae, much as in the formation of a swan-egg. Usually at first apex, slightly at one side there is visible a clear space, much like that at the dilated end of the swan-egg.
+
+![]() A B C D E F G
+
+Fig. 73.--A, odgonium of Odogonium stagnale (× 480). B, anthidium of the same species. C, anthidium of O. flavum (× 600). D, spermatoid of same species. E, F, fertilization in O. flavum; e.p., the spermatoid within the egg-cell; f., the spermatozoon entering the egg-cell. G, macrodrium with several dwarf males, attached to it (× 400). (C-F, after Klamath.)
+
+This is the "receptive spot," and it is here that the spermatoid penetrates the egg-cell. At maturity the odgonium opens, either by a pore near the top or by the filament bending somewhat and leaving the top of the cell open, just as when a swan-egg is laid. The spermatozoon then enters through this opening and is formed within the open space, and in this a pore is developed for the entrance of the spermatoid.
+
+Amheridium. The anthidium (Fig. 75, B, C) consists of a series of short cells, formed by the rapid division of a vegetative cell, with very little elongation of the daughter cells. These cells are often very small and may bear only one odgonium or they may be upon different ones. In the latter case, they are often very small male plants ("dwarf males"), which, growing from special swan-eggs (Androecia), attach themselves to the female plant.
+
+106
+
+106
+BOTANY
+
+There are usually two spermatocoids produced in each antheridial cell. These closely resemble the swarm-spores, but are much smaller, with little or no chlorophyll, and are largely made up of the nucleus of the mother-cell.
+
+![]() A, B, C
+
+Fig. 78. �� A, cell of *Fukiothora adomia* (× 75). B, aplanospore. C, germinating spore.
+
+Fertilization. — The spermatocoid enters the egg at the receptive spot, and quickly penetrates its envelope, which is fused with the egg-membrane. The egg-cell now secretes a firm membrane, which generally becomes dark colored, and the contents lose the chlorophyll and sometimes become bright red. Germination follows after a period of rest, by the liberation of the contents of the egg, in- to four swarm-spores, each of which then rises to a new plant.
+
+Coleochete. — The highest form of Conjugatae, without belonging to the genus *Coleochaete* (Fig. 77), one of which there are several species, is found in fresh water, usually attached to the leaves and stems of aquatic plants, such as Water-lilies, Rushes, etc., and other water-plant species (Fig. 77) are the only ones known to contain a single chromosome and chlorophyll. Each of many of the cells are curious hairs, with a terminal point by which the plant gets its name. Swarm-
+
+![]() A, B, C, D
+
+Fig. 71. — A, *Coleochaete* *seposita* (× 25). B, single cell with hair (× 300). C, vegetative cells and antheridia (× 200). D, young zoospores, op., imbedded in the thallus.
+
+![]() Og
+
+THE ALGAE
+107
+
+spores are formed singly from any cell of the thallus. In *C. scutata* the oogonia arise from the ends of the cells of the radially arranged branches, which make up the thallus is composed. These differ from the oogonia of *C. patens*, which has the branches free, and in which, instead of being a mass, the oogonia are free at the ends of the branches, and have a single egg enclosed by a spermatangia.
+
+The antheridia are the disk-shaped cells (Fig. 76, 77, C) are formed by the division of a single cell into two small cells, which are colorless, and each of which gives rise to a simple hyaline branch. The egg-pulse is produced by the antheridia are small rhombic cells on the ends of the branches. When this process is effected, the egg-cell develops a wall which is thin, so that short branches grow out from the cells adjacent to the oogonium, which form a cellular envelope, so that a "spore-fruit" is developed, con-
+taining one egg-cell surrounded by the sterile protective mantle of cells (Fig. 78). By means of these short branches, each spore-gene gives rise to a new plant. The germi-
+nation of the spore in *Colocheat* resembles closely the same process in the low-
+er forms of the plant, and it has been suggested a possible remote relation between the lower Monas (Hepaticae) and the Coniferoides.
+
+Classification of Coniferoides (Engler and Prantl, g)
+
+A. Isopomor. --- Gametes alike.
+Families: Ulvaceae, Ulvothricaceae, Chetophoraceae, Mycoi-
+deaceae, Cladophoraceae, Gomontiaceae.
+
+B. Oospore. --- Gametes differentiated into non-motile eggs and spermatangia.
+Families: Ophiolophaceae, Cylindrocapnaceae, Odgoniaceae,
+Colocheataceae.
+
+![]() A diagram showing the structure of *C. scutata*. A shows a single cell dividing into two smaller cells. B shows a single cell with two small cells developing from it. C shows a single cell with two small cells developing from it.
+![]() Fig. 76.--A branch of *Colocheat* patens, showing antheridium, surrounded by the cortex, r., developed from the adjacent cells. C, section of a germinative cell giving rise to a mass of cells. (After OLIVER.)
+
+![]() A diagram showing the structure of *C. scutata*. A shows a single cell dividing into two smaller cells. B shows a single cell with two small cells developing from it. C shows a single cell with two small cells developing from it.
+![]() Fig. 77.--A branch of *Colocheat* patens, showing antheridium, surrounded by the cortex, r., developed from the adjacent cells. C, section of a germinative cell giving rise to a mass of cells. (After OLIVER.)
+
+106
+BOTANY
+
+**Order IV. Conjugate**
+
+The Conjugates differ so much from the Chlorophytes that have just been considered that they are sometimes removed entirely from the Green Algae. They differ most in their reproductive cells, which are never ciliated, so that fertilization is usually effected by the formation of a tube connecting the similar conjugating cells. The plants are either unicellular or simple, consisting of one cell. The cell is always uninucleate, the nucleus occupying the centre of the cell, and connected with the peripheral cytoplasm by more or less evident cytoplasmic threads or bands. The chromatophores are large, or of various forms, flat plates, stellate masses, etc.
+Small bright drops (tannin vesicles) are often present in many species. The cell-wall is usually delicate, and the cells often secrete a gelatinous matter, in which they are imbedded, so that many of the plants are slimy to the touch.
+
+The Conjugates are widespread in fresh water, but they occur in fresh sea. They may be divided into two families, the Desmidiaceae and Zygnemaceae. A third family, Mesocarpaceae, is sometimes recognized.
+
+**The Desmidiaceae**
+
+The Desmidiae are unicellular Algae, often of exceedingly beautiful form.
+The simplest (Mesocarpon, Sirospora, etc.) consist of a single cell, with a delicate cell-wall. In the more complex forms (Fig. 78), the flat chromatophore, which occupies the long axis of the cell, and contains a chloroplast (Fig. 79.). A) The chromatophore is a spiral band applied to the inner surface of the cell-membrane.
+
+In most of these Desmidiae the cells show a remarkable symmetry. This is indicated by a division of the cell-wall into two valves, one of which overlaps the other, not unlike what is found in the Diatoms. The cell-contours also show a corresponding symmetry. There are usually two chromatophores, one
+
+![]() A: A small unicellular alga with a central nucleus and a few chloroplasts.
+![]() B: A conjugating pair of algae showing a tube connecting their nuclei.
+![]() C: A conjugating pair of algae showing a tube connecting their nuclei.
+![]() D: A conjugating pair of algae showing a tube connecting their nuclei.
+![]() E: A conjugating pair of algae showing a tube connecting their nuclei.
+![]() F: A conjugating pair of algae showing a tube connecting their nuclei.
+![]() G: A conjugating pair of algae showing a tube connecting their nuclei.
+![]() H: A conjugating pair of algae showing a tube connecting their nuclei.
+![]() I: A conjugating pair of algae showing a tube connecting their nuclei.
+![]() J: A conjugating pair of algae showing a tube connecting their nuclei.
+
+**Fig. 79.—A., *Mesocarpon muscicola* (×30).**
+(After De Bary.) B., *Pleurostium intermedium* (×30). C., *Eunotum pinne* (×30). D., *Eunotum pyrenoidale*; v., vacuole containing glycogen; p., pyrenoid; I., from above; II., from the side. The chromatophores are shaded.
+
+**Band applied to the inner surface of the cell-membrane.**
+
+THE ALGAE 100
+
+in each half of the cell (Fig. 78, D). These are often composed of several radiating plates, united at the axis of the cell. Pyramids are present, and in the chloroplasts of the Chlamydomonas (Fig. 79, A) they may be seen at each end of the cell a small vacuole, containing minute crystals of sub- stantia plane, which show an active dancing movement in the fluid within the vacuole. The movements of these crystals are in the same direction as the equator of the cell.
+
+Movement of the elements not unlike those found in the Diatoms may often be detected in the Desmidae, and are probably due to protrusions of protoplasm through minute openings in the cell-membrane.
+
+Cell-divisions in Desmidae, as well as in most forms, the cell- division is somewhat peculiar. While the nucleus is dividing, a short, cylindrical membrane is formed, just inside the place where the edge of the two valves meet, and between them apart. Next a ring of mitochonid is formed, running round the inner face of the cylindrical membrane, and this ring grows rapidly and cuts off a new cell from each valve. One of the original valves has already divided into two, and one of these divides again to go with each of the new cells. The result is at first two very asymmetri- cal cells, but soon two more symmetrical valves develop from the cylindrical membrane, rapidly grow, and in a few hours reach maturity. The characteristic sculpturing found on the surface of many desmidae is due to the fact that when each semi-cell also divides, and one of the new chloroplasts passes into each new cell, and thus two Desmids are complete.
+
+In some genera of Desmidae (e.g. Desmidium), after a period of rest, four to eight cells are formed by internal division, much as in the formation of swarm- spores from zoospores in Volvox (see under Volvox).
+
+In the higher types (e.g. Comatula) only the protoplasm of the conjugating cella unite (Fig. 80, C, D). Two cells approach each other, and may become so closely united that their outer walls appear to be fused together. The nuclei grow out from between the valves, and when these come together they fuse and form a short channel, into which pass the contents of both conjugating cells, leaving their nuclei behind. The conjugating cells then separate again, leaving a wall cell having spines projecting from it (Fig. 80, D). It has been found that
+
+![]()
+A: A small heart-shaped structure with a central hole.
+B: A similar structure with a central hole.
+C: A small heart-shaped structure with a central hole.
+D: A similar structure with a central hole.
+E: A small heart-shaped structure with a central hole.
+F: A similar structure with a central hole.
+G: A small heart-shaped structure with a central hole.
+H: A similar structure with a central hole.
+I: A small heart-shaped structure with a central hole.
+J: A similar structure with a central hole.
+K: A small heart-shaped structure with a central hole.
+L: A similar structure with a central hole.
+M: A small heart-shaped structure with a central hole.
+N: A similar structure with a central hole.
+O: A small heart-shaped structure with a central hole.
+P: A similar structure with a central hole.
+Q: A small heart-shaped structure with a central hole.
+R: A similar structure with a central hole.
+S: A small heart-shaped structure with a central hole.
+T: A similar structure with a central hole.
+U: A small heart-shaped structure with a central hole.
+V: A similar structure with a central hole.
+W: A small heart-shaped structure with a central hole.
+X: A similar structure with a central hole.
+Y: A small heart-shaped structure with a central hole.
+Z: A similar structure with a central hole.
+AA: A small heart-shaped structure with a central hole.
+BB: A similar structure with a central hole.
+CC: A small heart-shaped structure with a central hole.
+DD: A similar structure with a central hole.
+EE: A small heart-shaped structure with a central hole.
+FF: A similar structure with a central hole.
+GG: A small heart-shaped structure with a central hole.
+HH: A similar structure with a central hole.
+II: A small heart-shaped structure with a central hole.
+JJ: A similar structure with a central hole.
+KK: A small heart-shaped structure with a central hole.
+LL: A similar structure with a central hole.
+MM: A small heart-shaped structure with a central hole.
+NN: A similar structure with a central hole.
+OO: A small heart-shaped structure with a central hole.
+PP: A similar structure with a central hole.
+QQ: A small heart-shaped structure with a central hole.
+RR: A similar structure with a central hole.
+SS: A small heart-shaped structure with a central hole.
+TT: A similar structure with a central hole.
+UU: A small heart-shaped structure with a central hole.
+VV: A similar structure with a central hole.
+WW: A small heart-shaped structure with a central hole.
+XX: A similar structure with a central hole.
+YY: A small heart-shaped structure with a central hole.
+ZZ: A similar structure with a central hole.
+AAAAA: Four identical structures arranged in pairs along vertical lines (A-A-A-A).
+BBBBB: Four identical structures arranged in pairs along vertical lines (B-B-B-B).
+CCCCC: Four identical structures arranged in pairs along vertical lines (C-C-C-C).
+DDDDD: Four identical structures arranged in pairs along vertical lines (D-D-D-D).
+EEEEEE: Four identical structures arranged in pairs along vertical lines (E-E-E-E).
+FFFFFFF: Four identical structures arranged in pairs along vertical lines (F-F-F-F).
+GGGGGGG: Four identical structures arranged in pairs along vertical lines (G-G-G-G).
+HHHHHHH: Four identical structures arranged in pairs along vertical lines (H-H-H-H).
+IIIIIII: Four identical structures arranged in pairs along vertical lines (I-I-I-I).
+JJJJJJJ: Four identical structures arranged in pairs along vertical lines (J-J-J-J).
+KKKKKKK: Four identical structures arranged in pairs along vertical lines (K-K-K-K).
+LLLLLLLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLlLh
+
+
+Fig. 80.—A., cells of Gymnogyna Brebe- sovi; B., division (× 500); C., cell of Comatula; D., formation of the zygospore in Comatula ep. (× 600).
+
+110
+BOTANY
+
+the spore develops without the fusion of the nuclei, which takes place only just before the萌发期 begins.
+
+**Germination.** The fusion of the nuclei is followed by two successive nuclear divisions, but of the four nuclei thus formed only two persist, and there are but two new nuclei left to divide again into four, and so on. This is the case with the young Desmidia are somewhat simpler in structure than the mature forms, and it is not until after the second division of the young Desmid that the complete form is established. The young Desmidia are free from the thick membrane of the zoospores (Kabaho, 16).
+
+The Zygnemaceae
+
+The Zygnemaceae — "Pond-scums," as they are sometimes called — are among the commonest of the fresh-water Algae. They are evidently closely related to the simpler Desmidia, from which they have probably sprung, and from which they differ mainly in being united into long filaments. Their cell-structure corresponds closely with that of certain Desmidia. Thus Mocospermum resembles almost exactly a single cell of the filamentous genus Mocospermus (Mozgeozia), while Spirogyra is represented among the Desmidia by Spirotania, and Zygnema by Cylindrocystis.
+
+In Spirogyra, the commonest genus, the thin-walled cylindrical cells show a thin cytoplasmic layer lining the wall, and contain one or more ribbon-shaped spiral chromosomes, in which are very conspicuous pyrenoids, about which
+
+![]() A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
+
+Fig. 81. — A-C, conjugation in Spirogyra sp. (× 200). D, cell-divisions in S. crassa (× 175). E, zoospore of S. communis, showing the fusion of the nuclei. (E, after Overton.)
+
+110
+
+THE ALGAE
+111
+
+may usually be seen numerous starch-granules. The large nucleus is suspended in the centre of the central vacuole by protoplasmic filaments attached to the pyrenoid. The protoplast divides into two parts, which soon become normally light. After the nucleus divides, the protoplast is cut in two by a wall formed about the equator of the cell, and growing inward until the division is completed.
+
+**Conjugation.** -- Conjugation in the Zygnemataceae is very much like that in the Desmids (Fig. 81, A-C). From neighboring cells, either in the same filament or as adjacent cells in different filaments, two cells approach each other and fuse. The protoplast may leave both cells and unite in the conjugating canal, or, as in most species of Spirogyra, one of these cells remains within the other and the other passes through the canal to join the other cell. The contents of both cells pass into the cell-contents preliminary to their fusion, but in the Mesocarpaceae there is little or no communication between them. This is striking in this respect the behavior of the very similar Monosomion.
+
+As a rule, germination of the nuclei, so far as it has been studied, occurs soon after the fusion of the gametes. A fusion of the chromosomes takes place immediately in Spirogyra. The ripe zoospores lose their chlorophyll and become dark brown color, and its contents appear coarsely granular, owing to the accumulations of food material.
+
+The spores may retain their vitality for several years. On being placed in water they quickly absorb water, and within a week or so begin to show signs of life. The outer coat is colored, and growth begins. The outer membrane is ruptured, and the young plant pushes through the aperture. In Spirogyra (Fig. 82) the elongated primary cell tapers at its base, which is enclosed within the spore-membrane. The young plant will soon be seen, which gradually are used up as the young plant develops.
+
+Occasionally planospores (Fig. 83, D-E) are found, which closely resemble the zoospores except that they arise without fucundation.
+
+**Affinities of Conjugation.** -- The lower Desmids, both in their structure and reproduction, recall the simpler Volvoxaceae and Protoconocaceae, and are probably related to them. From these simpler Desmids more complex forms have arisen.
+
+The structure of the cell-wall, as well as the reproduction, suggests the Peridinids and Diatoms, which may also be remotely related to the Desmids. The resemblances, however, are probably only analogies.
+
+![]() Fig. 82.—Germination in Spirogyra longa (7). A, B & C.
+![]() A
+![]() B
+![]() C
+
+112
+BOTANY
+
+**Order V. Siphonae**
+
+Unlike the other Green Algae, most of the Siphonae are marine plants, being especially abundant in the warmer seas. They are characterized by the absence of vegetative cell-divison, so that the plant-body, which may often be of considerable size, is a tubular structure. The outer wall is thin and transparent, the thallus, and all parts of the internal cavity are in direct communication. The cytoplasm lines the interior of the tubular thallus, and in it are imbedded numerous nuclei and small chromatophores. It is doubtful whether the plant-body of the Siphonae can properly be considered a single cell, as is sometimes done. It seems better to look upon it as a "nucleocyte" - a cell complex, in which the division-walls are suppressed, and the protoplasm confluent.
+
+The Plant-body.---One of the simplest members of the order is Botrylloides, a common marine alga, extremely abundant growing upon wet clay. The plant consists of a pear-shaped, dark green vesicle, about one-half millimetre in diameter, which is fastened into the earth by a system of dichotomously branched colorless roots. A microscopic examination shows that all parts of the plant are in open communication. The cytoplasm lines the wall as a thin layer, in which may be demonstrated many small nuclei. The
+
+![]() A diagram showing a single cell with various parts labeled: A - nucleus; B - small round bodies; C - spore; D - spore; E - spore.
+
+Fig. 83. --- A, B, *Monoceros* sp., cells showing the single axial chromatophore.
+B, seen from the side; a, nucleus.
+The small round bodies are tannin vesicles.
+C, *Gonium* of *Monoceros* sp. (*x 300*).
+D, E, *Geniatemma* sp., showing siphono-
+spores (*x 300*).
+
+A
+B
+C
+D
+E
+
+THE ALGAE
+115
+
+chromatophore forms a more or less interrupted continuous thin plate, but may sometimes be replaced by numerous scattered chlorophyll bodies.
+
+A
+
+B
+
+C
+
+D
+
+E
+
+F
+
+G
+
+The other fresh-water genus, Vaucheria (Figs. 88, 89), consists of elongated tufts of filaments, occasionally attached by colorless roots, but quite as often floating in the water. The filaments branch irregularly, and may become contracted at the base, and separated into individuals. The chromatophores are small oval plates, with their long axes parallel with that of the filament. Drops of oil are often seen on the protoplasm, probably the product of the photosynthesis in the chromatophores.
+
+Marine Siphonous.—The most specialized of the Siphonous are marine, and include the spongy-looking Bryopsis (Fig. 85, A), and the spongy-looking Codium, are the best known from the temperate seas. In the tropics, especially about coral reefs, the Siphonous tend to great development. Many of these forms, like Halimeda (Fig. 86), Penicillia, etc., are heavily incrusted with carbonate of lime, and play an important part in reef-building.
+
+![]() A B C D E F G
+Fig. 84. — A, Botrydium granulatum (× 10). B, a young plant; C, D, germinating indecaspate spores (× 300). E, part of a mature sporangium (× 40). F, conjugating gametes (× 500). G, gametangium (× 300).
+
+![]() A B C D E F G
+Fig. 85. — A, Bryopsis phaeacea (× 7). B, Codium tempestivum; end of a filament with sporangium.
+sp. (× 50). C, gamete (?) (× 300). G, after THOMAS.)
+
+115
+
+114
+BOTANY
+
+In Caulerpa (Fig. 87) the plant resembles closely one of the higher land-plants, showing a creeping stem which projects from its lower side and leaves which grow from its upper surface. There is, however, no trace of cellular structure, the thick wall of the tubular thallus being supported by numerous threadlike braces, which are visible.
+
+In most of the large forms, like Codium (Fig. 85, B), Halimeda, and others, the thallus is composed of extensively branched, but nonsessate filaments, whose extremities are often composed of club-shaped, or sometimes conical cells, which form a sort of cortex, or rind, upon the outside, while in the central part the filaments are much more slender and loosely interwoven.
+
+Reproduction.—Non-sexual reproducion may be brought about by the separation of a portion of the thallus into a new plant of reproduction known in Caulerpa. In some species such plants are produced, and in some instances splan-
+6
+
+Fig. 86.—a. Halimeda manulis (× 1); b. longitudinal section, highly magnified.
+(After Miers.)
+
+shows that these are in pain, corresponding to the cells situated in the colourless superficial layer of protoplasm. In this case the giant sponoid is to be considered as a compound structure made up of manyiliate sponoids. The same applies to Caulerpa.
+
+Sexual Reproduction.—In Caulerpa no trace of sexual reproduction has been discovered. The gametes are very small and are produced in large numbers. In Botrydium very small gametes are produced from asexual spores, which form in great numbers at the end of the growing period. These become red in color, and sometimes form a brick-red film upon the ground where the plant has been growing. They germinate quickly, after a proper period of rest, and the con-
+
+THE ALGAE
+
+115
+
+tentia escape as numerous small biciliate gametes (F), which after conjugation germinate into new tentia. A similar, but more complicated, type of reproduction occurs in the marine algae, the Siphonaceae. In these, two kinds of cells are formed in special cells (Fig. 85, C). While the actual function of these cells is unknown, they may be regarded as the "egg" and "sperm" of the algae. The larger ones are green, the smaller ones yellowish, in color.
+
+The most highly developed reproductive organs occur in Vanhieria (Fig. 88, 89), where the egg-cell is a large, green, ovoid body. The spermatozoon, or egg-cell has lost the power of motion and is retained within the oogonium. The latter is an oval cell, with a more or less definite beak at the apex. The antheridium is a long, thin, often curved, cell, which may arise directly from a vegetative filament, or by way of a short stalk from the oogonium (or oogonia) upon a special branch (Fig. 89, B).
+
+The young oogonium contains numerous nu-
+clei, which are soon separated off from the filament, all of them then reunited into the filaments, resulting but a single nucleus in each cell when ripe; the latter opens at the apex, and a portion of the contents escapes to form the remainder forming the egg (Fig. 89, C, D).
+
+In this case only one cell which contains little or chlorophyll is produced; two or three minute spermatia are developed. They consist mainly of a nucleus, and possess two lateral flagella. These are very short and delicate. The egg now develops a thick membrane, loses its chlorophyll, and becomes a resting-spor. This germinates by sending out a germ-tube, much as does the nodose.
+
+Classification of Siphonaceae (Engler and Prantl, p.)
+
+As the development of many of the Siphonaceae is still imperfectly known, their affinities are still somewhat doubtful. The following families are recognized: Botrydiaceae, Phyllosporeaceae, Bryopodiaceae, Derbaceae, Vanhieriaceae, Caulerpaceae, Codiceae, Valoniaeae, Daryclaceae. The Botrydiaceae can be readily compared to the Protococcaceae while the other families are more closely related to some forms among the Conferoidae, especially the genus Pythophora. The affinities of most of the marine Siphonaceae are doubtful.
+
+Phyllosporeae. — A very remarkable form is the genus Phyllosporeum,
+which resembles in structure, Vanhieria; but it is a parasite within
+the tissues of a species of Aristrum. In habit it closely resembles
+
+![]() Fig. 87.—Cantarea placentae. (Natural size.)
+![]() Fig. 88.—Vanhieria sparsa.
+![]() Fig. 89.—Vanhieria sparsa.
+
+116
+BOTANY
+
+certain Fungi; and this, together with certain structural resemblances, suggests the derivation of some of the lower Fungi from Alga.
+
+Order VI. Characeae
+
+The Characeae, or "Stone-worts," as they are sometimes called, on account of the abundant deposit of calcium-carbonate in many of them, differ so much from the other Algae as to make their position in the system doubtful; but they are sometimes removed entirely from the Algae.
+
+The Characeae are, for the most part, fresh-water plants of moderate size, usually a few centimetres in length, and sometimes a metre or two in length. They all are much alike in structure, and the order is easily distinguished.
+
+The plants always grow from a single apical cell, and show a regular succession of lateral branches, with the lateral members growing in whorls from the nodes. The lat-
+![]() A diagram showing a cross-section of a Characeae plant.
+Fig. 88.--A, *Fucusaria sessilis*, with oogonium,
+sp., and antheridium, ex (× 300). B, *F. marina*,
+with stippled cells at the base of the lateral
+branches of *F. sessilis*. D, active, E, germinating
+nourous of *F. sessilis*.
+
+eral branches are typically of two kinds: branches of limited growth (usually called leaves) and a smaller number of branches which are, in their structure, en-
+tirely similar to the main axis from which they spring. The plant is fastened to the ground by numerous colorless roots.
+Cell-structures vary greatly in different species; some reach a very large size; the long internodal cells sometimes attain a length of ten centimetres or more, with a diameter of nearly a millimetre. In all of the cells exposed to the light there are numerous oval chromatophores, containing green or brown pigments (figs. 87, C).
+At one place, marking the boundary between the ascending and descending parts of the rotating protoplasm within the cell, is a
+
+THE ALOK 117
+
+strip quite destitute of chromatophores, known as the neutral zone, as here no movement can be detected. The cytoplasm forms a thick layer within the cell-wall surrounding the single, very large vacuole. The chromatophores are seen to move about in the outer layer with no movement; but below this a thick layer of soft, very granular protoplasm is seen to be in active rotating movement, the whole mass moving in a single current. Numerous large nuclei, as well as other protoplasmic bodies, some of peculiar form, like little spiny balls, are carried along in this protoplasmic current.
+
+![]() A diagram showing the development of the sexual organs. C, young algospore of V. clausii; the nuclei are shown black. D, an open algospore, with a single nucleus; n, sp., two sperms. E, conjugation of the sex cells.
+
+Wardel. In the young cells there is a single large nucleus, of the ordinary form, which divides by mitosis when new cells are formed. In the large cells, however, the nucleus undergoes repeated direct division, or fragmentation, resulting in numerous large nuclei, often of very irregular form (Fig. 90, B).
+
+Apical Growth. All of the leaves of the plant grow from an apical cell, which, in the larger shoots, has the form of a hemisphere (Fig. 90, B, e). From its base segments are cut off, in regular succession, by transverse walls. Each disk-shaped segment divides quickly by a second transverse wall, which is usually convex
+
+4
+
+118
+BOTANY
+
+upward, into an upper cell (x), from which the node arises, and a lower internodal cell (y), which undergoes no further division, but finally increases enormously in size. In many species of Chara the long internodal cell is covered by a cortex, or rind, but in the other genera this is wanting.
+
+All of the lateral organs are outgrowths of the nodes. The pri-
+mary nodal cell in the stem of Chara (Fig. 90, B, C) divides first by a vertical wall into equal parts. From these two cells, by repeated divisions, arise the lateral organs, which grow off, so that in a transverse section of the young node shows two central cells and a circle of peripheral cells of different ages. Each peripheral cell becomes the
+
+![]() A plant of Chara fragile (natural size). B, longitudinal section of stem- apex of Chara ap., x, apical cell; z, p, nodes and internodes of youngest segments; l, a leaf (× 300). C, cross-section of a young node. D, cross-section of older internodes showing the cortex of Chara fragile (× 300). F, older cortex of C. fragile. G, longitudinal section of young leaf.
+
+**Fig. 90.** Plant of *Chara fragile* (natural size). **B**, longitudinal section of stem-apex of *Chara* ap., x, apical cell; z, p, nodes and internodes of youngest segments; l, a leaf (× 300). **C**, cross-section of a young node. **D**, cross-section of older internodes showing the cortex of *Chara* fragile (× 300). **F**, older cortex of *C*. fragile. **G**, longitudinal section of young leaf.
+
+apical cell for a lateral branch or leaf, and divides very much like the apical cell of the main shoot, except that the divisions in the nodes are more numerous and that after some time the num-
+ber of segments have been cut off, cease to divide further, and elongates to form the pointed terminal cell of the leaf (Fig. 90, G).
+
+From the nodes the leaves lamellae are developed, which may,
+in some cases, be reduced to mere papillae.
+
+**Cortex.**—In most species of Chara the basal node of each leaf gives rise to two peculiar branches, which grow one upward and one down, closely appressed to the outer surface of the internodes, which they completely conceal. The growth of these branches, or corti-
+
+90
+
+THE ALGAE
+
+110
+
+cal lobes, is also apical, and nodes and internodes are developed (Fig. 90, E). The internodes, and sometimes the lateral nodal cells, become much elongated, and form the fluted cortex so conspicuous in Characeae. The cells of the cortex are often large, and may give rise to spines or bosses, which encircle the stem at regular intervals. Upon the outer surface of the cells carinate of lima is often present, deposited in large, irregular masses, which make the whole plant roughly globular.
+
+Branches arise from the leaves, or branches of limited growth, there are also formed branches like the main axis (Fig. 90, A). These always arise in the axil of the oldest leaf of a whorl (occasionally also from the axil of a leaf), and each branch replaces the upper cortical lobe of the oldest leaf of each whorl.
+
+Roots. — The roots consist of slender filaments, also showing apical growth, which grow from the lower stem-nodes. The cells are densest of chlorophyll, and the rotation of the protoplasm is exceedingly active.
+
+Reproduction
+
+No special non-sexual species occur in these plants. Special bud-like organs are sometimes developed from the old nodes, or upon the roots. These may be single cells, or multicellular bodies, with the cells filled with starch. Such resting-buds, or bulbils, give rise to new plants under favorable conditions. From almost any part of the plant, although usually from an old node, a new shoot grows out, so-called "Pro-embryo", simple filaments from which a new plant grows, much as it does in the germination of the resting-spore, and branches with unincorsted base sometimes become detached and form new plants.
+
+Sex-organ.— All of the Characeae show very highly developed sexual reproductive organs, anthidium and oogonium of great complexity, and not closely resembling those of any other plants. They are always found on one side of the stem (Fig. 91), and belong to the same type of growth. Their structure is very uniform throughout the order.
+
+In Nitella they ordinarily occur in pairs (Fig. 91 B) on the upper side of the leaf-nodes. A section through the young complex shows that the anthidium replaces a leaflet, and that the oogonium is an outgrowth of its basal node thus representing a leaflet of a lower order. In Nitella the anthidium is terminal upon a leaf, and the oogonium is terminal upon a node (Fig. 91 C).
+
+Anthidium. — The young anthidium (Fig. 91, C-E) consists of a basal node and internode, above which is the globular apical cell separated from the node by an intermediate segment. The globular apical cell divides longitudinally into equal parts; these next divide transversely, and again vertically, so that
+
+130
+BOTANY
+
+the body of the anthocidium is composed of eight cells. Each of these octants divide by a periclinal wall with one outer and two inner cells (Fig. 91, C), and the latter of these by a second periclinal wall into two more. Thus each octant is divided into three concentrically arranged cells (D). The cell between the body of the anthocidium and the periclinal wall of the first cell forms the cell of the anthocidium and becomes later very conspicuous (Fig. 91, E).
+
+As the anthocidium increases in size, the eight outer cells become much expanded laterally and form as many triangular plates, with deeply indented walls, constituting the so-called "shields," of which the anthocidial wall is made up. The chromatophores within these cells, as well as those in the second series of cells, the Mauviers, become of an orange-scarlet color as the anthocidium ripens.
+
+The Mauviers (Fig. 91, A, m), or second cell of each octant, remains undivided, increases much in length but very little in breadth, and forms a club-shaped cell attached to the middle of each shield and projecting into the cavity of the anthocidium.
+
+![]() A diagram showing the structure of an anthocidium.
+
+Fig. 91. - A, manubrium, m, of Chlorella, bearing numerous spermatous filaments attached to the capitulum, c (× 75); B, longitudinal section of a young leaf of C. vulgaris, showing a leaf-node with a leaf-plate (× 200); C, longitudinal section of a leaf-node of a leaflet, which is joined to a node of the leaf by the basal internode, y (× 300). C, D, E, development of the anthocidium, seen in longitudinal section (× 200); F, G, H, development of a ripe spermatous filament, showing the spermatocytes within the cells (× 800). D, free spermatocyte; E, free spermatozoon; F, spermatocyte; G, spermatozoon; H, spermatid.
+
+THE ALGAE 121
+
+The innermost series of cells undergo extensive changes. Each one usually divides into two, which are known as the "Capitula" (c), and from these bud new capitula, which also divide into two, and so on. The capitula may be a series of transverse divisions; or the branches may form secondary capitula, which in turn develop several (usually three or four) of the long fascicules (f). In each capitulum there is a single egg-cell, and in some species, especially in Nitella, there is developed a single large spermatocyst (G, H). These arise mainly from the nucleus of the operculum by its becoming elongated and coiled, but in the two species figured here they are formed directly from the cytoplasm.
+
+When the antheridium is quite ripe, the shields separate, and expose the filaments to the water, and the slender, spirally coiled spermatocysts escape through a pore in the wall of the operculum.
+
+**Oogonium.**—The oogoni- um, in Chara (Fig. 92), represents a single cell, which grows from the basal node of the antheridium. It is a short cell, with a basal node, and incinoderm. The former consists of a cen- tral cell surrounded by five elongated cells. The latter elongate and form a covering about the spindles of the oogonium proper. The five elongated cells which surround the oogonium are spirally twisted, and from the upper part of each of them arises a stalk, with which the others form the five-celled crown at the top (Fig. 93). In Nitella (Fig. 94), a second crown-cell is cut off from each of the long cells, so that the crown is composed of two tiers of cells.
+
+From the base of the oogonium in Chara a flattened cell (Fig. 92, c) is cut off, and in Nitella two or three such cells are produced. These are egg-cells and contain large starch-granules, and is filled with large starch-granules and oil-drops, which make it very opaque. The upper part, however, is comparatively free from granular contents, and forms the receptive area.
+
+Peristomial Cells. When ready for fertilization, the long cells about the oogonium separate from each other below the crown, with a slight elongation at this point. Five clefs are thus formed below the crown through which the spermatocysts enter the space above the apex of the oogonium. The wall of these latter becomes softest at the apex so that the spermatocysts penetrate into them with great ease; and when fusion takes place between an egg-cell and a spermatocyst, it is found that both become hard and woody, and sometimes the walls also are silicified. As at the fruit ripens, the chro- matophores sometimes become red or yellow. Finally the outer
+
+![]()
+A C D E cr cr cr
+B x
+
+
+**Fig. 92.—A-D,** development of the oogonium in Chara (after Wettstein). A, young oogonium (section × 300). B, young oogonium of Nitella (× 300). O, egg-cell; e, enneacelle.
+
+
+**Fig. 93.—A-D,** development of the oogonium in Chara (after Wettstein). A, young oogonium (section × 300). B, young oogonium of Nitella (× 300). O, egg-cell; e, enneacelle.
+
+
+122
+BOTANY
+
+cell-membranes of the sheathing cells decay, leaving the hardened inner walls projecting from the surface of the spore like the threads of a worm.
+
+The ripe spore-fruit falls to the bottom of the water, and after a few weeks is capable of germination. The spore-content first divides by a transverse wall into a large basal and a smaller apical cell. The latter contains but little food, grows rapidly, soon divides again by a vertical wall into two cells, one of which elongates, bends down and forms a root, fastening the young plant to the mud. The other cell (Fig. 93, A, st.) develops phloem and xylem upward, and by repeated divisions gives rise to a short, simple filament --the Pro-
+meristem-- of the pro-embyro. This develops two nodes, from the basal one (Fig. 93, D) of which roots are devel-
+oped, while from the upper node formed a whorl of branches, one of which soon assumes the character of the perfect shoot, the origi-
+nal pro-embyro not developing any further (Fig. 93, E, f, k).
+
+![]() A diagram showing the germination process of Chara sp., showing stages of pre-embryo: r, primary root (× 60); z, second stage; sp, sporophyte; rn, rhizoid; k, root-node; x, axis which is to form the permanent axis (× 60); C, spore; A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y.
+
+**Classification of Characeae** (Engler and Prantl, p.)
+
+Two families of the Characeae are recognized, but they are very closely related.
+
+In the Nitellinae, represented by the genera Nitella and Tolyppella (Fig. 94), the stem is always without cortex, and the oogonium has ten cross-walls. In the Characeae, with which we are concerned in this work is Chara, there are but five crown-cells, and a cortex is generally present.
+
+In one species of Chara, *C. crinita*, the oospores are developed with-
+out fertilization --one of the few well-authenticated cases of par-
+thenogenesis.
+
+---
+A
+B
+C
+D
+
+THE ALGAE
+123
+
+**Affinities of Characeae**
+
+The Characeae show no very evident affinity with any other group of plants. Perhaps, on the whole, they most nearly resemble some of the Siphonaceae, but the relationship, if it exists, is very remote. Certain resemblances in the reproductive organs have suggested a possible affinity with the Mosses, but this is, to say the least, exceedingly problematical.
+
+**Fossil Characeae.** — Abundant remains of Characeae are found fossil, but not in the older formations, and all remains so far discovered are closely related to existing forms, and throw no light upon the origin of the group.
+
+**Class II. Phycophyceæ (Brown Algae)**
+
+Except the Diatoms and some of the Peridiniae, which may possibly be very remotely related to the true Phycophyceæ, the Brown Algae are essentially marine organisms. Of these, the Red Algae, make up the bulk of the shore vegetation of the Ocean. Among the Phycophyceæ few families approach the giants of the vegetable kingdom.
+
+Color. The Brown Algae, as their name indicates, possess, in addition to the chlorophyll, one or more brown or yellow pigments, of which two are demonstrable, phycoxanthine and phycoerythrin; the latter being soluble in fresh water. The mixture of these pigments has been termed "Phycophyllin."
+
+*Plant-body.* — None of the true Phycophyceæ are unicellular, the simplest being cell-rows, as in Ectocarpus, or flat disks (e.g. Pyrococelis).
+
+![]() A
+A
+
+![]() B
+B
+
+![]() C
+C
+
+Fig. 90.—A. Tolypella sp. (× 20). B. Nitella sp.
+C. Chara coriacea (× 40). V., oogonium ; S., antheridium ;
+S., gametangium.
+
+124
+BOTANY
+
+The larger Kelps and Fucaceae have a highly developed body, with a leaf-bearing axis suggestive of the flowering plants. Between these extremes are found the intermediate forms, which are flexibly attached, the holdfasts, or hapteres, of the larger forms being stout branched roots, which anchor them very securely (Pl. 2). In many of the larger forms, air-vesicles are developed which act as floats, and in the case of some of the smaller forms, they are used to propel the plant, where they may be exposed to the action of the light. While the leaves of these Algae are structurally very different from those of the vascular plants, they serve the same purpose, being true assimilators.
+
+In size, some of the Kelps rival the giants among terrestrial plants. The great Bladder-kelp, Nereocystis (Fig. 98), of our own Pacific coast is sometimes forty to fifty metres in length, but is exceeded by several species growing on the coasts of other oceans along nearly the whole Pacific coast, and in the south Atlantic, and is said to attain a length of two hundred to three hundred metres.
+
+Distribution. The Phaeophyceae are generally distributed throughout the ocean, but are perhaps more abun-
+dant in the cooler and temperate waters, thin being especially true of the warmer seas. Those found on the other hand, are common in the warmer seas. Many species, espe-
+cially in colder regions, grow where they are exposed to heavy surf for several hours at a time. Such forms are tough and leathery in consisten-
+ce, and develop a large amount of mucilage within their cells which prevents rapid loss of water.
+
+The Pacific coast of North America is especially rich in Phaeophyceae, especially in California, where a number of peculiar genera occur.
+Some of these, like the curious "Sea-palm" (Padina palmiformis) (Fig. 97), are so small that they are exposed to heavy surf, and we find in these forms an extraordinary development of the holdfast. A
+number of these genera belong to which the best known is the Gulf-
+weed (Sargassum bacciferum), of the
+
+![]() A diagram showing a cross-section of a kelp frond.
+A B C D E
+
+Fig. 98. - A, *Ectocarpus granulosus* (301; ep., sporangia; $n$, a small broom-like structure; $m$, more or less magnified. C, D, *Phaeophyllum* (after Sartwell).
+
+98
+
+THE ALGAE 125
+
+warmer Atlantic, are found floating in great masses. It seems still somewhat questionable whether these masses are derived from originally floating plants, or whether they spend their whole existence floating on the surface.
+
+Cell-structure. - The simpler Phaeophyceae are composed of mostly uniform cells, uninucleate, and within their cell-membrane several chromatophores are contained. These cells are usually but rarely elongated, somewhat ribbon-shaped. Rarely but single chromatophore is present. Sometimes, as in Ectocarpus, pyreoids like those of the Chlorophyceae are present.
+
+Among the highly developed large Kelps and Fucaceae, the tissues
+
+![]() a
+![]() b
+![]() c
+
+Fig. 98. -- a, Sphaerocystis alicina, top of filament; b, c. cirruses, showing unicellular sporangia; c, the same, showing pluricellular sporangia. (After BURKART.)
+
+are correspondingly well developed, assimilating, conducting, and mechanical tissues being constructed.
+
+Reproduction. -- Among the same development of the reproductive parts is seen as we have observed among the Chlorophyceae; but on the whole, notwithstanding their very highly developed vegetative structures, the reproductive organs are simple. In the Chlorophyceae, as in many laterally attached clima, occur in many of them (Fig. 99, D), but are not known in the Fucaceae, the highest order. In some of the orders they are the only forms of reproductive cells known, this being the case in all of our large Kelps.
+
+Where sexual reproduction is possible they are always mixed into the water when fertilization is effected. There is much the same
+
+136
+BOTANY
+
+evolution of the sexual cells that is found in certain groups of Chlorophyceae. Thus in Ectocarpus (Fig. 95) the gametes are entirely similar; in Cutleria (Fig. 100) both gametes are motile, but one is much larger than the other, while in Fucus (Fig. 104) there is still greater difference between the two.
+
+The zygote developed from the union of the gametes grows at once into a new plant. The Phaeophyceae, never being exposed to complete dessication or to great changes of temperature, do not need to develop resting-spores, such as characterize most of the fresh-water Chlorophyceae. The Phaeophyceae are divided into two orders, Phaeosporeae and Cyclosperae.
+
+Order I. Phaeospereae
+
+**Ectocarpaceae.** — The family Ectocarpaceae include the simplest of the Phaeo-
+sporeae. Of these the genera Ectocarpus and Pythiales are perhaps the best known. These plants are attached by a short stalk to some suitable sub-
+stance, which are sometimes prostrate and creeping, but more commonly are erect. Their leaves are either lobes or somewhat irregular bands in which are embedded conspicuous chloroplasts.
+
+The plants branch extensively, the cells at the ends of the branches being often elongated and tapering, while those near the base of the branches are shorter, where the cells are usually shorter. In some of the larger forms, slender branches grow downward from the base of the lateral branches and form an apical cell-row (Fig. 96).
+
+**Spalacelariaceae.** — In the Spalacelariaceae the growth is apical; the apical cell-row is formed by a single cell, and this cell may even show the beginning of the lateral branches before any other change has taken place (Fig. 96). In the segments cut off from the apical cell longitudinal rows of smaller cells may be formed, so that the plant-body is no longer a simple cell-row as in Ecto-
+carpaceae.
+
+**Laminariaceae.** — The commonest and largest of all the Phaeo-
+phyceae are the Laminariaceae, or Kelp Plants, which grow on rocky coasts in the cooler seas, and reach an extraordinary development upon our own Pa-
+cific coast, where a number of species occur. In the Atlantic the various species of Laminaria are the common repre-
+sentatives of the family; but in the Pacific, in addition to Laminaria,
+
+![]() A diagram showing a plant with natural size; r., holdfast; b., older plant with young leaves.
+Fig. 97.—A. *Egregia Monostachy*, young plant, natural size; r., holdfast; b., older plant with young leaves. I.
+
+---
+
+PLATE II
+
+Postelvia palmiformis, a characteristic Kelp of the Californian coast. (Photograph by Dr. W. R. Shaw.)
+
+![]() A black and white illustration of two kelp plants with long, thin fronds. The plant on the left is smaller and has a more rounded shape, while the plant on the right is larger and more elongated.
+
+THE ALGAE 127
+
+there are the giant Kelps (Lessonia, Nereocystis, Macrocytis, etc.) as well as other genera (e.g. Egregia [Fig. 97], Postelasia) which are quite unlike each other.
+
+The plant in all of these forms is very large and shows a high degree of differentiation. In Laminaria it consists of a cylindrical stalk expanding above into a leaflike lamina, and attached by a large root-like holdfast. Similar to Laminaria, in general structure, are Egregia (Fig. 97) and Alaria, which have in addition to the
+
+![]()
+A B
+
+
+Fig. 96. - A. Nereocystis Lütkeana, young plant, reduced; r. holdfast. B. Macrocytis pyrifera, tip of branch, showing the growing-point (1<\x>); v., air-venices.
+single leaf-like lamina, numerous small lateral leaves growing from the stem. In Egregia some of these are sporophylls, and some are modified into air-venices.
+
+Lessonia and Macrocytis branch extensively, and reach a very large size. Nereocystis (Fig. 98), a very conspicuous Kelp of the northern Pacific, has an enormously long stem, tapering to the large holdfast, and having the holdfast upper portion enlarged at its upper end into a globose mass of cells as a croquet ball. To this are attached large leaves, three or four metres long.
+
+![]()
+A B
+
+
+128
+BOTANY
+
+Tissues of Laminariaeae. -- The tissues of the Laminariaeae are well developed. The outer tissues are composed of small, closely set cells, which contain numerous chromatophores, and constitute the assimilative tissue. Within this tissue are found many large, elongated cells, which contain but few chromatophores. The central part forms a sort of pith with loosely woven elongated cells, some of which are elongated elements, closely resembling the sieve-tube of the higher plants (Fig. 90). The inner tissues are parenchymatous.
+
+The outer tissue are generally tough and flexible, so that the plant can endure the beating of the surf without being injured (Fig. 90).
+
+The formation of the leaves is in many cases the result of a splitting of an old leaf to produce a new one, as very clearly shown in Macrocyptus (Fig. 98, B). The sickle-shaped terminal portion of each branch consists largely of actively growing tissues. Short slits appear at regular intervals, which extend until they reach the margin and thus form a leaf. As the young leaf grows, its length enlarges at its base while it is at first solid, later developing into the pear-shaped float which is found at the base of the older leaf.
+
+![]() A diagram showing the structure of a leaf from Laminaria. It shows A - outer tissue of leaf, more highly magnified; B - sporangia and paraphyses per sporangium; C - sporangium; D - spore; E - paraplastid; F - sporangium with paraphyses.
+
+Fig. 90. -- A. *Nereocystis Lutkeana*, transverse section of leaf, showing sporangia, sp.
+B. outer tissue of leaf, more highly magnified.
+C. sporangia and paraphyses per sporangium.
+D. spore.
+E. paraplastid.
+F. sporangium with paraphyses.
+(× 500).
+(× 1000).
+(× 1000).
+(× 1000).
+(× 1000).
+(B after Rauw.)
+
+Reproduction
+
+Most of the Phaeosepores give rise to biciliate zoospores, which are formed in the so-called unicellular sporangia (Fig. 90, C). The nucleus of the sporangium divides repeatedly, and this is followed by the division of the cytoplasm, but no cell-walls are formed. The zoospores are usually oval or kidney-shaped, and have two lateral
+
+THE ALGAE 129
+
+Cilia. In the Kelps the sporangia are formed in dense masses (Fig. 98, A), either on the ordinary leaves, or upon special sporophylla.
+The sporangia are usually of two kinds, zoospores and zoosporic cysts, or paraphyses. These are the only reproductive bodies known in the Laminariaceae.
+
+In many of the Phaeophyceae, however, there are formed the phycoblasts or sporangia, or perhaps more correctly, gametangia, as it seems probable that the cells developed from these are gametes. In Ectocarpus the young gametangium is a short lateral branch, divided transversely into several cells (Fig. 98, C, D). In these, series of protuberances arise from the sides of each cell, and give rise to a chain of nearly cubical cells, each of which gives rise to a biciliate cell, much like the non-sexual zoospores, but probably always incapable of developing further without fertilization, although this has only been observed in one case.
+
+The resulting zygote germinates at once, as do the zoospores.
+
+Germination. — So far as the development of these forms has been followed, the germinating spore develops first a cell-row, which, in the larger forms, like the Ectocarps, produces a flat thallus. This thallus is one of the most important characters of the mature plant. Nemocystis (Fig. 98, A) will illustrate the more important points.
+
+The young plant is first produced by the branching of the lamina and above it the expanded lamina. The point of most active growth is at the junction of the stem and lamina.
+
+Here, by active growth, the first indication of the future leaf arises. This is very active at the base of the lamina, which soon splits along the middle line into two equal parts. These divide repeatedly in the same way until a bunch of leaves are finally produced.
+
+In some of the perennial forms, like Laminaria, which recur through life each year, as Laminaria, the stem increases annually in thickness, and a section shows a series of rings curiously like those in the woody stems of the higher plants.
+
+The Cutleriaceae
+
+Intermediate in some respects between the typical Phaeophyceae and Fucaceae is a small family, the Cutleriaceae. The
+Fig. 100.—Cutleria multifida: a., female sexus; b., male sexus; highly magnified.
+(other Monax.)
+
+130
+BOTANY
+
+plant-body in Cattalia (Fig. 100) is a flat, dichotomously branched thallus, growing by intercalary divisions, much as in the Ecto-ar-
+paceae. Zoospores, like those of the other Phaeosporeae, are formed,
+and the gametangia are very similar, but are of two kinds, producing
+gametes of very unequal size, although both male and female
+gametes are ciliated.
+
+Order Cycloporeae
+
+The Fucaceae comprise the most specialized, and next to the Lami-
+nariaceae, the largest of the Phaeophyceae. They are distinguished
+by having the egg-cell very much larger than the spermatangia, and desti-
+tute of zoospores.
+The best known of these are the Rockweeds of the genus *Fucus*, which are
+widely distributed through the colder waters of the northern hemisphere. An-
+other familiar form on our northern Atlantic coast is *Ascophyllum nodosum*,
+whose slender rubberlike
+fronds, at intervals, hang
+down from the rocks at low tide. In the warmer
+seas the Fucaceae are rep-
+resented by numerous
+genera, the largest being
+*Sargassum*. *S. bacciferum*,
+the Gulfweed, is common
+floating in the Gulf Stream.
+
+The species of Fucus
+(Fig. 101.) *A.* *Fucus vesiculosus* H. C. Holmberg.
+Gonodendron; v., vesicula; con., conopodium.
+
+is a stout stalk, which is attached by a disk. The branches are either
+nearly cylindrical or, in some species, flattened with a prominent midrib between them. The leaves are simple in some species, little tufts of fine hairs scattered over the thallus, and these are found to project from small pits (Cryptostomata), within which
+
+![]() A diagram showing three different views of a plant body.
+![]() B A diagram showing a different view of a plant body.
+![]() C A diagram showing another view of a plant body.
+
+THE ALGAE 131
+
+their bases are concealed. Similar cryptostomata have been found in some of the Phaeospores.
+
+In Sargassum (Fig. 102) and Cystophyllum the much-branched axis has attached to it long leaf-like appendages, so that the appearance of the plant is much like that of the ordinary terrestrial flowering-plants. Where air-venules are present they may be bored in the thallus, as in *Fucus* *vesiculosus* (Fig. 101, A), but are, as a rule, short lateral branches, as in most species of Sargassum (Fig. 102).
+
+Apical Growth.--Growth in the Fucaceae is apical and due to the division of a single large cell at the apex of each branch. This cell is usually situated at the bottom of a little pit at the end of the branches. The cells which form these pits are of the form of a truncated wedge, whose outer face is obtuse, the inner one being convex and inclined to the broad surface of the branch. Segments are cut off from the inner truncating edge.
+
+The cells divide rapidly and produce a mass of small-celled tissue surrounding the apical cell, which gradually pass into the tissues of the older parts.
+
+The tissues of the mature parts closely resemble those of the Kelp. There are several layers of small cells joining the outside tissues, and these contain most of the chlorophyll. The cells are thin-walled, and their cell-walls are highly gelatinous. Sieve-tubes may also be present.
+
+Reproduction.--None of the Fucaceae develop zoospores, but small pieces of the plant may become detached and form new individuals.
+
+The sexual organs are antheridia and oogonia, borne in pits much like those in which the cryptostomata are formed. These conceptacles are usually formed upon somewhat modified portions of the plant-body. In *Fucus* the fertile branches have their ends very much enlarged, and in Sargassum there are special fertile branches developed. The formation of these conceptacles is indicated by the presence of antheridia and oogonia, which may be formed either as conceptacles (in different plants) as in *Fucus vesiculosus* and Halidrys; or they may be borne in the same conceptacle (*Fucus fistigatius*).
+
+Antheridium.--The antheridia in *Fucus* (Fig. 104, D, E) are small oval cells borne at the ends of branches or some of the hairs within the conceptacle. They
+
+![]() Fig. 105.--Sargassum sp.; e., air-bubbles. (About natural size.)
+131
+
+182
+BOTANY
+
+closey resemble in their structure the unicellular sporangia of the Kelp. The nucleus of the young antheridium divides repeatedly, and three following divi-
+sion of the cytoplasm into as many parts as there are nuclei. The spermatocyst (H) has a large nucleus and an orange-red pigment-spot, so that in mass the whole appears to be a deep reddish-orange color. This color makes it easy to recognize the spermatocyst of this di-
+cious species.
+
+The antheri-
+nia are very much larger than the antheridia, and have a bright dark olive-green color. They arise directly from the cells forming the base of the antheridium. The conceptacle and not from the base of the antheridium. The antheridium divides into a basal cell and a ter-
+minal cell, which is the antheridium proper. At first the cell is colourless, but it becomes green when filled with olive-green or brown chromatophores as it devel-
+ops. The terminal cell divides, probably in all cases, into two equal parts, but in some species into a smaller number (Fig. 103). In
+Halidrys there is but a single egg in the oogonium. In all the forms that have been thoroughly investigated, the nucleus divides into eight, whether the full num-
+ber of eggs or half of them appear at any one time.
+
+Fertilization. When ripe, the reproductive organs are easily broken away, and when exposed to the water, which happens in those forma growing between tide-marks when the tide rises, the wall of the oogonium or antheridium is dissolved, and the productive cells are exposed to view. The eggs are in two forms. The sperma-
+tonoids have two laterally inserted cilia, one being often longer than the other. They collect about the eggs, and sometimes in such numbers that the egg is made to rotate by the movement of their cilia. A spermatozoon then enters through one of these cilia into the egg, where it fuses with the nucleus (Fig. 104 J). The egg is then invested with a membrane, becomes pear-shaped, and attaches itself by the pointed end. Cell-division now proceeds rapidly, and in time an apical cell is established, but the details are still not quite clear.
+
+The attached egg forms a holdfast, and the upper part develops into the branched thallus.
+
+![]() A diagram showing a cross-section of a growing-point of a plant.
+A B
+
+Fig. 103. — *Pleurococcus.* d., growing-point of a plant; e., a spadel cell of the new shoot; b., cross-section of the growing-point; z., the apical cell (cf. Fig. 104).
+
+183
+
+184
+
+THE ALG.E 183
+
+While most of the Fucaceae are attached, Sargassum, Cystophyllum, and some others are found floating and vegetating freely far from any land. It is still uncertain whether or not some of
+
+![]()
+A - A. Fucus serratus.
+B - B. Cystophyllum (x 100).
+C - egg-cells escaping from the oogonium.
+D - filament, with asteridia.
+E - asteridia, more highly magnified.
+F - F. resellus, oogonium discharging the egg-cells.
+G - fertilization of the egg-cell by the sperm-cell.
+H - young zygote.
+I - young zygote, showing division of the sexual nuclei; e. egg-nucleus; sp. sperm-nucleus.
+J - young zygote of Desmophyllum nodosum, with dividing nucleus.
+K - K. after FLAXER.)
+
+
+these species may spend their whole life as free-swimming or pelagic forms. These floating masses of seaweed serve as shelter for a great variety of marine animals, small fish even being found living in them.
+
+183
+
+134
+BOTANY
+
+Affinities of Phaeophyceae
+
+The Phaeophyceae must be considered to be a highly specialized group of plants, whose peculiarities are largely due to their essentially marine mode of life. They are very different in most respects from the Chlorophyceae, and it is quite possible that they have had an evolutionary history distinct from that of the other algae. Between the zoospores and gametes of the Phaeophyceae and some of the brown Peridiniaceae suggests the possibility of their having originated from some such forms, which might bear somewhat the same relation to them that the simple Volvocaceae do to the other Chlorophyceae.
+
+Classification of Phaeophyceae (Engler and Prantl, 9)
+
+**Class PHAEOPHYCEA**
+
+**Ord. I. Phaeoporee.** Producing both zoospores and gametes, the latter always motile.
+a. Gametes similar. Families: Ectocarpaceae, Sphaecelaceae, Laminariaceae, etc.
+b. Gametes unlike. Families: Cutleriaceae, Tilopteridaeae.
+
+**Ord. II. Cycloporee (Fucacee); no zoospores. 2 gametes non-ciliated.**
+Fam. I. Fucaceae.
+
+Dictyotales (Williams, 39)
+
+This small group of marine Algae is probably related to the Phaeophyceae, and might perhaps be included in that class. The plants grow from a definite apical cell and do not reach a large size, nor is it known whether they reproduce sexually or asexually like the higher Phaeophyceae. Until recently, it was supposed that their reproductive cells were always destitute of cilia, and for this reason they have sometimes been included with the Rhodophytaeum. Recently, however, it has been shown that both sexual and non-sexual reproductive cells are formed, the former showing great difference in size between the male and female cells (Fig. 105).
+
+**Class III. RHODOPHYCEA (Red Algae)**
+
+The Red Algae comprise the majority of seaweeds, but in size they are much inferior to the Phaeophyceae. Most of them inhabit salt water, but a number of genera are found in fresh water, usually in cold, rapid streams, or on rocks washed by falling water. In size they range from almost microscopic forms to stout plants a metre or more in length.
+
+![]() A diagram showing the structure of a red alga.
+
+THE ALGAE
+13b
+
+Color. — The characteristic red color is due to the presence of a red pigment, phycoerythrin, which occurs in the chromatophores with the chlorophyll. This pigment is soluble in fresh water, and forms a rose-red solution which is strongly more or less approaching greenish yellow by reflected light. The pigment varies in amount, being least developed in the fresh water species, which are generally blackish or olive-green, resembling in color the Cyanophyceae. The marine species exhibit all shades from delicate rose-red to blackish purple.
+
+Chromatophora. — The chromatophores, except in the Bangiaceae, which are not closely related to the other algae, are usually small, oval disks, several in each cell. Just what the relation of the phycoerythrin is to the chlorophyll is not clear, but it is evident that it modifies the light-rays, as it is found by experiment that the rays most efficient in photosynthesis are those of the violet end of the spectrum in the Rhodophyceae than they are in the Chlorophyceae. The phycoerythrin no doubt neutralizes the absorption of certain rays in the passage of light through the water, where these plants grow in deep water.
+
+Plant-body. — Some of the Rhodophyceae are simple filaments (Griffithia), or branched filaments, as in Callithamnion. A thin, flat thallus is found in Grimerlia and Porphyra, while some of the forms living on land, such as Chondrus or Gigartina, are tough and leathery in texture like some of the Kelpa. Much more rarely there is an incrustation of lime, and the plants become of stony hardness. This occurs in the peculiar Combines.
+
+Cell-structure. — With the exception of the Bangiaceae, which are sometimes removed from the Rhodophyceae, the protoplasts of adjacent
+
+![]()
+a) A diagram showing a female Diptota dichotoma.
+b) A diagram showing a male Diptota dichotoma.
+c) A diagram showing a female Diptota dichotoma highly magnified.
+d) A diagram showing a male Diptota dichotoma highly magnified.
+
+
+
+136
+BOTANY
+
+cells are connected by very evident protoplasmic filaments (Fig. 106). There is a large pit in the middle of the division-wall, which is closed by a thin membrane. The protoplasts of the plant of a mutant somewhat like the musilage masses in the sieve-tubes of the higher plants. The actual communication is effected by delicate pores around these plates, through which fine threads connect the neighbouring cells.
+
+In the young cells there is always a single nucleus, but the older cells, which are often large, frequently possess numerous nuclei. The cell-walls show a tendency to become gelatinous, and there may be developed an abundant intercellular gelatinous substance in which the cells appear to be imbedded.
+
+![]() A diagram showing the connection between the protoplasts of young, mature, and tetrasporangia of C. fusiformis.
+
+**Apical Growth.** — The growth of the plant is, with few exceptions, apical. In the more delicate forms there is a single apical cell; in the larger ones there may be a group of these (e.g. Champia). When there is a group of these, it can usually be shown to be composed of extensive branched filaments, which are separated by the tenuous intercellular substance, and in such cases each of the individual branches has its own apical cell. Ordinarily the cells divide no further, but in Nitophyllum and the Corallines there are intercalary divisions.
+
+**Reproduction**
+
+A marked characteristic of the Rhodophyceae is the complete absence of ciliated cells. Non-sexual reproduction is usually effected by the so-called Tetraspores, which, as their name indicates, are formed
+
+THE ALGAE
+
+157
+
+in groups of four within a mother-cell. In a few cases, e.g. Chan-
+transia, Monosporae are formed, and very rarely the sporangia de-
+velop more than four spores (Callithamnion dasyoides).
+
+Sexual reproduction in the sexual reproductive organs are special
+cells, Carpospore cells which are produced by the carpospore
+matia). The carpospore may at once give rise to a mass of spores
+(carpospore), or it may be associated with other cells into a multi-
+cellular organ, the Procarpy, which after fertilization develops into a
+complex of cells. In the Chlorophyceae, the resting-spores and tetra-
+forms will be taken up in connection with the special orders. As
+in the Phaeophyceae, no resting-spores are produced, and both tetra-
+spores and carpospore terminate as soon as they are ripe.
+Chlorophyceae. — The Chlorophyceae include the Chlorella, the
+Bangiales, with a single order, Bangiaceae, and the Florideae, which
+comprise the greater part of the class, and differ so much from the
+Bangiales that the latter are sometimes considered to be more nearly
+related to the Chlorophyceae than to the Florideae.
+
+Bangiaceae.
+
+The Bangiaceae comprise a small number of simple Algae, which,
+aside from their color, show certain resemblances to the Chlorophy-
+cea, and may perhaps connect these with the higher Rhodophyceae.
+While most of them are marine, there are also a number of fresh-
+water species.
+
+Plant-body. — The plants are either filaments or very simple cell-plants, as
+in Porphyra (Fig. 107), which except for its color closely resembles Ulva. The
+leaf-like structures of some species are composed of two or three con-
+nections can be discerned between the cells.
+
+Reproduction. — The sexual reproduction takes place in the escape of the con-
+tent of a thallus-cell either directly, or after one or two preliminary divisions.
+These monospores thus closely resemble the monospores of many Converta-
+ces, from which they differ only in being larger and more numerous. The
+anemoid, or creeping, movements have been detected, in which they are dif-
+ferent from the monospores of the Florideae. The sexual reproduction is also very
+simple, and no special organs have been observed.
+
+There is no contraction of the contents, and a slight prominence is developed,
+which perhaps represents the trichogyne, or fertilizing-tube leading to the con-
+tents of the monospore (Fig. 107 A). The Carpospore (Fig. 107 D).
+
+The Anthelia (Fig. 107 C) are formed from vegetative cells by a
+division into a number of small cells which lose their color, and both in pos-
+ition and structure are very similar to those in the disk-shaped species of Colo-
+chloa (see Fig. 108). The monospores are globular spermatia. When one of these comes in contact with the pro-
+jection from the carpospore it fuses with it, and the contents pass into the
+carpospore. This process is repeated until all the cells of the carpospore
+which closely resemble the non-sexual spores, and like them terminate as soon
+as they are set free.
+
+138
+BOTANY
+
+Affinities of Bangiales
+
+Aside from their color, and the absence of cilia in the reproductive cells, the Bangiales recall certain Coniferaceae, especially such forms as Coleochaete, and it is by no means impossible that they connect these with the higher Rhodophyceae, although this view must be considered for the present as nothing more than a conjecture.
+
+THE FLORIDEA
+
+This is the largest group of Algae, and includes the greater number of the common Seaweeds.
+
+![]() A diagram showing the structure of a Floridean plant.
+
+Fig. 107. - A. *Porphyra* sp., plants growing upon a leaf of *Phytodendron* ; z, young plant (Natural size); B, cells from the thallus of *P*. *sulphurea* (*x* 600). C. *Anthocerium* sp., young plant of *Gigartina* *sparsa*, showing fertilization; sp., spermatium (*x* 600). D. *D*, after Berthelot.
+
+The Plant-body. - In a few forms, like Grifithsia, the plant is a simple cell-row, but usually it is either a branching filament or a broad thallus of some size. The Floridea, however, are inferior to the Phaeophyceae in this respect, and are all simple.
+
+Apical Growth. - With few exceptions the growth of the plant is apical. Where it is a simple or branching filament the apical cell is elongated, and has here segments cut off from it which undergo no further division. In other cases, however, such as *Chlamys*, in others, such as *Polysiphonia* (Fig. 111), the segments cut off from the base of the conical apical cell here undergo further longitudinal divisions, whereby the outer vertical cells are cut off from the axial row of cells. In other forms, e.g. *Chlamys* (Fig. 116), there is a group of initial cells at the apex of the thallus.
+
+THE ALGAE 139
+
+**Tetrasporae.** — In most of the Florides the non-sexual reproductive cells are tetraspores. These are formed in special cells, which may either project as short branches (Fig. 106) or are formed from an inner cell of the thallus. Not infrequently the groups of tetraspo-
+rangs are found upon short branches of the thallus. Tetrasporae are wanting in some species of the genus *Florideae*, e.g. *Nemalion*, but they may be replaced by monosporae (*Batrachospermum*) (Fig. 109), where they are borne upon a special non-sexual plant, which was described as another genus, *Chara*. This is, unfortunately, so far as that it was independent.
+
+In this case the sexual plant (*Batrachospermum*) develops as a special branch from the Chara-form, somewhat as the perfect Chara-plant arises from the pro-embryo.
+
+![]()
+A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
+
+
+Fig. 108. — *A.* *Nemalion multifidum.* (Natural size.) *B.* *N.* *Anderomii.* (Natural size.) *C.* *Chara* *sp.,* thallus, branch with anthocysts. *D.* (*x* 800). *E.* tetrasporangium on branch (*x* 300); *F.* tetrasporangium. *E.* young gonimoblasts, or spore-fruits; *g.* older gonimoblast.
+
+Tetraspores may be formed by successive division of the mother-cell, or by a simultaneous division of the protoplast after the nucleus has divided into four. Sometimes (e.g. *Corallina*, Fig. 115) the tetraspores are arranged in a row (zonula).
+
+**Classification** (Engler and Pranti, 9)
+
+As already stated, there is a good deal of variation in the charac-
+ter of the sexual organs in the Florides, and upon this this division into orders is based. Four of these orders are usually recognized,
+
+14
+
+140
+BOTANY
+
+viz. Nemalionales, Gigartinales, Rhodymeniales, Cryptonemiales.
+These are further divided into about twenty families.
+
+Order I. Nemalionales
+
+These are the simplest of the Florideae, and include most of the
+fresh-water species. They are usually densely branched Algae, but
+may develop a tubular thallus as in Lemnaceae and other genera. In
+the fresh-water genera the color is usually blackish or olive instead
+of the red of the marine genera. The commonest of the fresh-water
+forms are Bartrachospermum and Lemnaceae.
+
+![]() A
+![]() B
+![]() C
+
+![]() D
+![]() E
+![]() F
+![]() II
+![]() III
+
+Fig. 108. — A, *Bartrachospermum vagum* (× 50). B, fertilized carposporium; on,
+sporium; ep, spores developing from the carposporium. C, *Chantrenia macrospora* (× 300). D, *Lemna minor* (× 100). E, *Lemna gibba* (× 100). F, single monosporangium (× 500). G, geminating monospore. (B, after Davie.)
+
+Reproduction.—In most of the Nemalionales non-sexual reproductive cells are unicellular or are monospores, although tetraspores are known in some of the marine genera.
+
+The sexual reproductive organs are the carposporium and anthidium, which are readily studied in Nemalion (Fig. 108). The carposporium is a flask-shaped cell at the end of a branch. The anthidia are groups of small globular cells also at the end of short branches. Each anthidium-cell produces a single
+
+THE ALGAE
+141
+
+globular spermatium, naked at first, but later developing a delicate membrane.
+This comes in contact with the trichogyne, and its contents pass into the carpo-
+gonium. The latter then becomes a spore-fruit, which is a large cell, and this cell does not develop into a spore, as in the other Algae, but begins to grow and divide, forming a mass of cells, which are all connected by a common wall. This mass of cells, the whole structure being known as the "Spore-fruit," or Sporangium.
+The spore-mass may in some forms be surrounded by a loose envelope of branches developed from the cells in the vicinity of the carpogonium.
+
+![]()
+A: A Rhodonia emera (natural size); ep, cystocarpe.
+B: Gigartina spinosa, plant with cystocarpe, reduced about one-half.
+C: Endoclada vernicata, procarp; mea, auxiliary cell; t, trichogyne.
+(After HAVRENSCH.)
+
+
+Order II. Gigartinales
+
+The Gigartinales are mostly Algae of comparatively large size and coarse texture. Many of them, e.g. *Chondrus crispus*, the "Irish Moss," and various species of *Gigartina* (Fig. 110, B), grow attached to rocks or stones by means of long rhizoids. They are often gelatinous and cartilaginous in texture, due to the large development of the gelatinous intercellular substance. Owing to this some of them are utilized to some extent for food. The tetrapores are usually buried in the thallus. The archesporia form patches of small superficial cells, each of which gives rise to a spermatium.
+
+Order III. Sphaeropleales
+
+The Sphaeropleales are a small order of Algae, represented by two genera, *Sphaeroplea* and *Euglena*. The former is a very small green Alga, with a spherical body covered with minute scales or plates. It is found in fresh water and is used as a food for fish. The Euglenas are also small green Algae, but they have no scales on their bodies. They are found in fresh water and are used as food for fish.
+
+142
+BOTANY
+
+The carpogonium in the Gigantaceae is the end-cell of a short branch which is buried in the thallus (Fig. 110, C), but the trichogyne projects above the sur-
+face, so that it may be fertilized. After fertilization the carpogonial cell comes into contact with a neighboring cell (Auxiliary cell) from which the spores are developed. The auxiliary cell is a mere tube of the outside wall is formed, the whole constituting the cystocarp.
+
+Order III. Rhodiales
+
+This order is the largest, and includes the majority of the most beautiful species; these the carpogonium, as in the last order, is the end-cell of a special branch, and is connected with the auxiliary cell (or cells), and often with the beginning of the cystocarp-wall, into the so-called Procarp. This is seen in its simplest form in the genus Calithamnion (Fig. 112, D).
+
+One of the cells of the filament sends out a short branch of two cells, the upper one develops into a thallus, while in the lower one at its base, on either side of the carpogonial branch is found a large cell (x), which after the fertiliza-
+tion of the carpogonium divides into two cells (y). These two cells become the auxiliary cell, and a smaller basal one which develops no further. The car-
+pogonium, after it is fertilized, divides into two cells (x', c'), each from each of these a small lateral cell (a) on each side to connect with another cell into which its nucleus passes, but does not fuse with the nucleus of the auxiliary cell,
+which remains passive, although very active in growth. In the divisions which follow and gradually develop into a mass of spores, the nuclei remain separate until division of the nucleus which came from the carpogonium, so that they are direct descendants of the ferti-
+lized carpogonial nuclei. There
+are also many cases of spores on opposite sides of the cell from which the carpogo-
+nium was derived.
+
+The common genus Poly-
+siphonia may be taken to represent the more special-
+ized reproductive organs of
+the Rhodiales.
+
+The hairs which bear the antheridia (Fig. 111, A) are forked, and one of the branches develops into an antheridium, while the other grows into a slender
+
+![]() A diagram showing parts of a plant structure.
+
+Fig. 111. -- Polysiphonia sp. d., tip of branch with young antheridia. x (× 500). B, older an-
+theridium; I, from within; II, optical section;
+c', apical cell.
+Antheridia and procarps are borne upon the hairs,
+which grow from near the apex of the shoot.
+
+143
+
+THE ALGAE
+143
+
+hair, apparently attached to its base. The young anthocidium shows a definite apical growth, the segments dividing into a central cell and a series of peripheral cells, the latter dividing into many small cells, each of which produces a single spermatium. The apical cell persists as a large transparent cell (x) at the apex of the tip.
+
+*Procarp.* — The procarp, also, is formed upon a hair, but this is not usually forked. The procarp develops from the second cell of the hair. This cell divides transversely, forming two cells, one of which grows downward toward the shoot, i.e. the inner one—gives rise to a short carpogonial branch, usually of four cells (Fig. 112, B). The two posterior cells undergo but little change, and help to form the wall of the cystocarp, which covers its greater part by the two lateral branches of the carpogonial branch. The outer branch is bivalve shell, and completely enclosing the carpogonial branch, except for the long trichogyne. The auxiliary cell (x) arises by a transverse division from the cell from which the carpogonial branch grows out. This auxiliary cell is cut off from the carpogonium, which fuses with the auxiliary cell, this latter fusing with the neighbouring cells of the carpogonial branch, and thus forms the outer layer of the cystocarp. The latter consists of the centre of the young spor-ar-ruit, and from it the large pear-shaped spores are budded off. The wall of the cystocarp finally forms an urn-shaped envelope enclosing the spores (Fig. 115). The development of the sporocarp in Rhodophyta is very similar.
+
+![]()
+A C E x
+B D t
+I II
+
+
+Fig. 112.—A-C, *Polypodium* sp. *A*, very young procarp (optical section) (*× 800*). B, two sections of an older procarp: I, medium section; II, superficial cells; c, carpogonial cell; x, auxillary cell; o, anterior cell of the joint. C, fertilized procarp (optical section); x, long trichogyne; t, long trichogyne; e, long trichogyne; d, long trichogyne; e, long trichogyne; f, long trichogyne.
+
+
+114
+B/ITALY
+
+**Order IV. Cryptonemiales**
+
+In the Cryptonemiales the auxiliary cells are often remote from the carpogonium branch, and from the carpogonium there grow out filaments which fuse with the auxiliary cell. This has been especially noted in the genus Dendranaea (Fig. 114).
+
+The trichogyne in this genus is extremely long and often branched. Fertilization is effected as usual, and the base of the carpogonium grows off from the trichogyne.
+
+The carpogonia then develop two or three slender branches ("eporo- phores"), each of which contains a nucleus. The sporogenous filaments grow later divided into two or more cells.
+
+The auxiliary cells are cells of branches at some distance from the carpogonium, and the sporogenous filaments grow until they reach these cells, when fusion takes place between them and the auxiliary cell. Not infrequently the filament grows, and reaches another, or even two or three other auxiliary cells, but in this case there are as many cells in the sporogenous filament as there are auxiliary cells.
+
+An enlargement forms at the point of junction of the sporogenous filament and the auxiliary cell (Fig. 114, B), and the upper part of this is cut off by a wall, the lower part being connected to the rest of the sporogenous filament, and not from that of the auxiliary cell. From this cell, by repeated division, numerous spores, so that a single fertilization results here in a number of spore-fruits, while also, however, all connected with the carpogonium by the sponogenous filaments.
+
+**Corallium.** — In the peculiar family, the Corallinae, very extensive cell-fusion follows the fertilization. In Corallinae the reproductive bodies are borne in cup-shaped receptacles at the ends of the branches (Fig. 115). A great many carpogonial branches are formed near together, and after fertilization numerous filaments of the protoplasts of these branches, as well as of the neighboring cells, and from the large multinucleate fusion-cell resulting, the spores are finally produced.
+
+![]() A diagram showing a longitudinal section of a young cystocarp. The cystocarp is shown with its central cell (A) and surrounding cells (B). The central cell has developed into a sporophore (C) with several branches (D). The cystocarp is shown with its central cell (E) and surrounding cells (F). The central cell has developed into a sporophore (G) with several branches (H).
+
+![]() Longitudinal section of a young cystocarp. The cystocarp is shown with its central cell (A) and surrounding cells (B). The central cell has developed into a sporophore (C) with several branches (D). The cystocarp is shown with its central cell (E) and surrounding cells (F). The central cell has developed into a sporophore (G) with several branches (H).
+
+![]() Longitudinal section of a young cystocarp. The cystocarp is shown with its central cell (A) and surrounding cells (B). The central cell has developed into a sporophore (C) with several branches (D). The cystocarp is shown with its central cell (E) and surrounding cells (F). The central cell has developed into a sporophore (G) with several branches (H).
+
+![]() Longitudinal section of a young cystocarp. The cystocarp is shown with its central cell (A) and surrounding cells (B). The central cell has developed into a sporophore (C) with several branches (D). The cystocarp is shown with its central cell (E) and surrounding cells (F). The central cell has developed into a sporophore (G) with several branches (H).
+
+THE ALGAE 146
+
+**Nature of the Spore-fruit**
+
+In the lowest of the Rhodophyceae, the Bangiaceae, a direct com-
+parison can be made between the product of fertilization and the
+spores of the Chlorophyceae.
+
+The division of the
+cuboid into sporophyte is
+directly comparable to
+the germination of the
+germination-spore in the
+Chlorophyceae.
+A
+
+In the Florideae, how-
+ever, no resting-spore is
+produced, but the en-
+capsulated sporophyte
+into a mass of spores by further growth, as in
+Nemalion, or trans-
+fer the nuclei to auxiliary
+cells, which are stimu-
+lated into growth and
+produce the spores. Oth-
+erwise, these processes
+have been important in
+explaining the process
+of fertilization and the
+structures developed
+from the fertilized carpo-
+genium as a new plant,
+— "Sporophyte," —
+parallel to that of the higher plants. All of the nuclei of the sporophyte are derived from the carposporial nuclei, and when the spores are derived from the auxiliary cells these seem closely related to those of the sporophytic nuclei, as the nuclei of the auxiliary cells do not enter into the structures of the sporophyte, which grows to some extent as a parasite upon the sexual plant, or gametophyte.
+
+**Affinities of Rhodophyceae**
+
+The Bangiaceae, as already intimated, show evident relationships with the Chlorophyceae, and perhaps connect them with the Flori-
+
+![]()
+A diagram showing the structure of a sporophyte in the Bangiaceae. The diagram includes various parts labeled: C - Cuboid; D - Division; E - Enveloping; F - Encapsulated; G - Growth; H - Hormone; I - Infection; J - Junction; K - Keratin; L - Layer; M - Membrane; N - Nucleus; O - Organ; P - Parasite; Q - Quiescence; R - Resting; S - Spore; T - Tube; U - Unit; V - Vegetative; W - Water; X - Xylem.
+
+
+Fig. 114. — *Dundespora parviflora*. A. fertilized carposporium sending out from the base the fine
+filament (a) which grows into auxiliary
+cells, e.g., B. gomphidium, or spore-fruit, pro-
+duced from the union of the filament and auxili-
+ary cell (b). C. The spore-fruit (c) with its
+spores (d), and (e) a section through it.
+
+
+146
+BOTANY
+
+dem. The latter must be regarded as an extremely specialized group without any near affinities with other plants.
+The same has recently been shown among certain Fungi (Ascomycetes) a type of reproduction strikingly similar to that of the Rhodophyceae, and it has even been suggested that the two groups may be related. This is, however, not generally admitted, and at present the higher Rhodophyceae must be considered to be widely separated from all other plants.
+
+Fossil Rhodophyceae
+
+Some of the Corallinæ, which have a heavy incrustation of calcareous matter, have been very perfectly preserved in a fossil condition; but the fossil forms are all alike, like the existing ones, and throw no light upon the origin of the group.
+
+The living genus Lithothamnion is common in the Mesozoic formations, but there are other genera which are much older.
+
+BIBLIOGRAPHY
+
+*94.* 1. Balsajeff, W. Uber die Bau und Entwickelung der Spermatozooiden. Flora, 1894 (supplement).
+
+*97.* 2. Balsajeff, W. On the Structure and Development of Gracilicola Americana. Ann. of Bot., XI. 1867.
+
+*98.* 3. Chester, G. D. Notes concerning the development of Nematalia multiseta. Bot. Gaz., XXII. 1896.
+
+![]() a diagram showing a cross-section of a coral-like organism with spiny projections.
+Fig. 115.—Corallina Mediterranea: a, section of corallium; b, cystocarpic conceptacle. (After Tawney and Bonner.)
+
+THE ALGAE
+147
+
+94. 4. Davis, B. M. Notes on the Life History of a Blue-green Mottle Cili.
+Bot. Gaz., March, 1860.
+
+95. 6. — On the Alga, a new Alga-like Organism. Ann. of Bot., VIII, De-
+cember, 1864.
+
+96. 6. — The development of the cystocarp in Chlamys parvima. Bot. Gaz.,
+XXI, 1869.
+
+97. 6. — Fertilization of Bartrachospermum. Ann. of Bot., X, 1869.
+
+98. 6. — Kerminierung der Tiercormenentwicklung bei Corallina. Ber.
+der Deutschen bot. Gesellschaft, XVII, 1869.
+
+![]()
+a b c d e f g h i j k l m n o p q r s t u v w x y z
+
+
+Fig. 138.—Chlamys parvima, a, b, c, d, successive stages in the germination of
+carpospore; e, spirospore; f, further stage in separation of spores; g, longitudi-
+nal section of apex of young plant. (After Davis.)
+
+
+99.-100. 9. Engler and Prantl. Die natürlichen Pflanzenfamilien. I Theil.
+2 Abs. Alge, 1860-67. Chlorophyceae, N. Wille; Phycophyceae,
+Drepanothaliae, H. Winkler; Rhodophyceae, A. Fritsch; Falken-
+berg, F. Hauptfleisch. This contains a full bibliography.
+10. Falkenberg; See Engler and Prantl.
+
+91. Falckenberg, H.; Engler and Prantl; New England Coast Washing-
+ton, 1861.
+
+92. 12. Farlow, E.B., and Williams, J.L. Contributions to our knowledge
+of the Phycomes. Phil. Trans Royal Soc., London, Ser. B, vol.
+190, 1868.
+
+93. 13. Goebel, H.; Outlines. Oxford, 1887.
+
+94. 14. Goebel; Organography. Vol. I. Oxford, 1890.
+
+95. 15. Haupfleisch; See Engler and Prantl.
+
+96.-97. 93a; 93b; H.Winkler; H.Winkler; Zygomen, Pfringhamhauz, Jahrb. f. Wiss.
+Bot., XXIII, XXIV, 1861-1862.
+
+98. 17. Klebs, G.; Uber die Fortpflanzungsphysiologie der niederen Organis-
+men.. Jena, 1866.
+
+
+
+148
+BOTANY
+
+79. 18. Luernsen, Ch. Handbuch der Systematischen Botanik, Vol. 1. Leipzig, 1876.
+95. 19. Miers, G. Guide to the Study of Seaweeds. London and New York, 1866.
+90. 20. Nott, C. P. The Anthoceris of Champia purpurea. Bryophyta, IV, 1866.
+97. 21. Oken, F. S. Die Systematische Botanik. Berlin, 1867.
+90. 22. ———. Phylomycetes of California. Proc. Cal. Acad. of Science, 1900.
+95. 23. Overton, C. E. Ueber den Conjugationsvorgang bei Sporogonia. Ber. d. Deutsch. Bot. Gesellschaft, VI, 1868.
+95. 24. Overton, C. E. Die Entwicklung der Sexualorgane bei Colocotaceae pulchrae.
+98. 25. ———— Die Entwicklung der Sexualorganen bei Colocotaceae pulchrae.
+98. 26. ———— Zur Entwicklungs geschichte der Fließleien. Bot. Zeit., 1868.
+95. 27. Oberhout, W. J. V. On the Life-history of Rhodobionia tenera. Annals of Botany, XIX, 1868.
+95.—98.— Phillips, R. W. Studies on the Development of the Cystocarp of Bryophytes and Lichens (Phytolacca). Journ. Bot., 1868.
+90.—98.— Saunders, De A. Physiological Memoirs, Proc. Cal. Acad., 3 ser.
+Botany, I, No. 4, 1868.
+90.—93.— Schimper, A.F., on the Distribution of Laminariaceae Transc Connecitans Acad., V, S, 1868.
+93.—94.— Schwabe, H., on the New Genus of Velatineae, Proc.Gas., XIX, 1868.
+93.—94.— Schwabe, H., on the Development of the Cystocarp of Grifithia Bor- netiana Bot Gaz., XXII, 1868.
+91.—34.— Solms-Laubach, Il Comt., Botany Oxford, 1861.
+97.—34.— Solms-Laubach, Il Comt., Botany Oxford, 1861.
+93.—36.— Stahlmanns Beiträge zur Botanik Berlin, 1867.
+93.—37.— Van Tieghem, Ph., Traité de Botanique Paris, 1867.
+90.—38.— Sturtevant, J., A Manual of Systematic Botany London and New York, 1865.
+93.—39.— Willis, N., See Engler and Prantl.
+90.—40.— Willdenow's Reproduction in Dictyoptera dichotoma Annals of Botany, XII, 1868.
+97.—41.— Wilmot F., Fresh-water Algae of North America Bethlehem, Penn., 1867.
+94.—42.— Dasmidse of North America Bethlehem, 1864.
+
+![]() A page from a botanical text book.
+
+CHAPTER VI
+
+THE FUNGI
+
+The Subkingdom Fungi includes a very large number of plants, nearly forty thousand species having already been described. These differ primarily from the Algae in being destitute of chlorophyll, but there are also very marked structural differences. Owing to the absence of chlorophyll, they are unable to manufacture their own food, and the absence of chlorophyll is not, probably, a primitive condition, and they are presumably derived from algal forms with chlorophyll.
+
+Doubleness many of the peculiarities of the Fungi are secondary ones connected with their parasitic habits. They are all saprophytes upon organic food. A small number of Fungi, the Phycomycetes, show more or less obvious evidences of their algal ancestry, but much the larger number have become so modified as to leave little or no traces of their algal origin among other plants. Where the Fungi lives upon dead matter, it is known as saprophyte; where it attacks living plants or animals, a parasite.
+
+A few Fungi are aquatic; but most of them live either within the bodies of their hosts or within the nutrient medium upon which they feed.
+
+Parasitism. — Many Fungi, such as the Rusts, Smuts, and many Mildews, are absolutely dependent upon living organisms, so-called "duplicates." The Smuts and Rusts are parasitic on plants; namely, a saprophyte may assume parasitic habit; i.e. it becomes a "faculative" parasite. While some species of Fungi are dependent upon a specific host, more commonly they may grow upon several — sometimes even different — kinds of plants. The Mildews are parasites of Bats, in the course of their development live upon two hosts, often quite unrelated. Thus the Cedar-cast (Gymnosporangium) passes part of its life upon the Red Cedar, and part upon the Craspedia or Haworthia. The Smut (Ustilago) is a parasite like the Tinea; it resembles like the behavior of certain animal parasites like the Tapeworm and Trichina, which live successively in the bodies of different hosts.
+
+Sympatosis. — A special form of parasitism, called Sympatosis, is exhibited by certain Fungi which live in symbiosis with other organisms are the Lichens, where a Fungus is intimately associated with an Alga, upon which it is parasitic to a greater or less extent, but to which it affords shelter, and probably certain food-elements, so that the association is to some extent mutually advantageous.
+
+148
+
+160
+BOTANY
+
+**Mycorrhiza.** — It has been found, also, that the roots of many of the higher plants are infested by a Fungus, whose delicate filaments apparently serve the purpose of root-hairs; the Fungus apparently receives its nourishment from the plant, and is attached to the roots with which it is associated. These Root-fungi have been named Mycorrhiza, but as they are always sterile, it is not known with what other Fungi they are related.
+
+**Pseudomonas.** — These are very injurious to the host, and are the common causes of plant diseases. Their growth within the tissues of the host not infrequently causes an abnormal growth of its cells, causing gall-like swellings, as in the case of the Cedar-rust already mentioned. The Pseudomonas is a saprophyte, and is due to the action of certain secretions (enzymes) similar to those by means of which the Fungus is enabled to dissolve and penetrate the cell-walls of the tissues in which it is growing. It is thus that some germinating spores find their way through the outer cells of the host and reach the inner tissues.
+
+**Fermentation.** — Fungi which live upon dead matter, by its decomposing position play a similar though less important role to that of the Bacteria in organic decomposition and nutrition. One characteristic form of organic decomposition is the alcoholic fermentation of sugar solutions through the agency of certain low Fungi, especially the Yeast-fungi.
+
+**Structure of Fungi**
+
+A small number of Fungi are unicellular, but much the larger num-ber are composed of filaments, or "Hyphae," which are massed into the vegetative body, or "Mycelium," upon which are borne the vari-ous reproductive bodies. The mycelium may be a delicate weblike structure, or the hyphae may be densely matted together so that the mycelium appears like a mass of cotton wool.
+
+In the Phycyomycetes, the hyphae are nearly or quite undivided, but the hyphae of the higher Fungi are divided by transverse septa, which are generally formed in regular succession from an apical cell.
+
+Cell-wall. — The cell-wall of fungi is usually made up of ordi-nary cellulose; but as it becomes older, there is usually a change into fungus-cellulose, which differs slightly from that of the green plants. In some cases, too, it becomes very hard, and the Fungus may be almost entirely surrounded by it, as is seen in the so-called sclerotium of the Ergot of Rye, for instance.
+
+Protoplast. — The protoplasm may fill up the cells completely, but usually there are large vacuoles. No chromoplasts are present, and the nuclei are small, and often difficult to demonstrate, but not essentially different from those of other plants. In the very long
+
+THE FUNGI
+151
+
+undivided hyphae of some of the Phycomycetes, active streaming of the cytoplasm can sometimes be demonstrated. Where the hyphae are colored, this may result from a coloration of the cell-wall, as in Alcyonium, or from the presence of pigments within the cyto-
+plasm, e.g. the scarlet pigment of species of Perizma.
+
+**Mycelium.**—The mycelium may live but a few days, or it may grow indefinitely. The mycelium of some species of Toadstools, where the mycelium is buried in the ground, continues to spread, giving rise to successive crops of the fruiting bodies.
+
+The hyphae of the fruiting structures are usually more compact, and often grow together, so that a section has the appearance of a true parasitic plant.
+
+**Reproduction.**—The lower Fungi, or Phycomycetes, resemble cer-
+tain Algae in their reproduction. They may form free-swimming zoospores, which produce spores similar to those of the Green Algae. The more typical Fungi, however, differ much in their reproduction from any green plants, and it is very hard to make any comparisons between them. A great variety of non-sexual spores are produced, which generally differ much from those of the Green Algae. These non-sexual spores are therefore best considered in connection with the special groups to which they belong.
+
+**Sexual Reproduction.**—Sexual reproduction is known for only a small part of the Fungi, and has been apparently quite lost in a very large part of the group. In some of the Phycomycetes, fertilization is effected much as in the Green Algae, in the more specialized Fungi the reproductive organs are more like those of the Red Algae, and as in these organisms fertilization is effected by a com-
+plicated spore-fruit, or sporocarp, from which the spores are produced secondarily. With very few exceptions, fertilization is effected by direct conjugation of the antheridium with the carpogonium, or by means of non-mobile spermatia like those of the Rhodophyceae.
+
+**Affinities of Fungi**
+
+A small number of the Fungi, the Phycomycetes, or Alga-Fungi, show a more or less evident resemblance to some of the Chlorophy-
+cea, and perhaps have some such relation to them as do such color-
+less parasites or saprophytes as the Dodder, or Indian pipe, to their remote relatives. But many other Fungi show no such affinities.
+Parasitic Algae like Phyllospthon, or Mycoides, make the derivation from Algae of quite colorless forms, or Fungi, by no means improbable.
+
+The greater number of Fungi, the Eumycetes, show much less evidence of being derived directly from algal ancestors, and their affinities are in most cases very obscure.
+
+153
+BOTANY
+
+Classification of Fungi (Engler and Prantl, 4)
+
+The Fungi are divided into three classes,— Phycomycetes, As-
+mycoetes, and Basidiomycetes; the two latter constitute the larger
+group of the Eumycetes, or True Fungi.
+
+**Class I. Phycomycetes**
+
+The Phycomycetes, or Alga-Fungi, include a number of plants
+which, while not all evidently related among themselves, show more
+or less affinity with the Green Algae, from which they have probably
+sprung. In few forms, the Chytridines, are either unicellular, or
+produce only imperfect spores; but in most others develop thick-walled
+hyphae, which are non-septate, like the filaments of the Siphonae.
+The Phycomycetes are either saprophytes or parasites, attacking
+both animals and plants.
+
+The Phycomycetes are divided into two groups, the Oomyctes
+and the Zygomycetes, the former showing a difference in the size of
+the gametes, which in the Zygomycetes are alike.
+
+**Subclass I. Oomyctes**
+
+The simplest of the Phycomycetes are the Chytridines, many of
+which are aquatic, parasites upon various Algae. Others attack
+many Flowering Plants, sometimes causing a good deal of damage.
+A common example of the former group is seen in species of Chytri-
+dium, often called "slime-molds" (Fig. 17), which live on the leaves
+of various species of Oleagineous plants. The Fungus produces small
+uniculate swarm-spores which on germination send a short germ-
+tube into the cell of the host. The body of the swarm-spore then
+develops into a large multicellular mycelium from which new swarm-
+spores are produced. At certain times, thick-walled resting-spores are pro-
+duced, apparently non-sexually, and these in time give rise to new
+zoosporangia.
+
+A somewhat more complicated form is the genus Polyphaea. *P. Plesios*
+(Fig. 17) is found in fresh water lakes and ponds. It attacks *Eucra-
+rea viridis*, whose enclosed cells it attacks and destroys. The zoospores of the
+parasite on germination send out delicate threadlike germ-tubes, which pene-
+trate the walls of the host-cells and grow through them. The body of the swarm-spore increases rapidly in size at the expense of the host-cells,
+and finally sends out a large satellite growth into which the contents pass,
+and finally develops into a new swarm-spore. This is a simple form of sexual reproduction, by which an oogonium and antheridium are
+formed, the latter issuing with the oogonium, which develops a resting-spore.
+This on germination develops a zoosporangium, much like that formed from
+the ordinary zoospore.
+
+Order I. Chytridines
+
+THE FUNGI 158
+
+Of the forms attacking the higher plants, the commonest belong to the genus Synchytrium. *S. papillatum* is sometimes very common in California upon *Erodium cicutarium*, whose leaves become covered with minute, white, spherical bodies, which are produced by the enlargement of the epidermal cells which are infected by the parasite. The reproduction is by zoospores, much as in Chytridium, but no sexual organs are known.
+
+![]()
+A - A chytridium cell, zoosporangium, sp., attached to the epidermis of Erodium cicutarium.
+B - Zoospore.
+C - E. Polyphaga Eugeniae.
+D - zoospore attached to a resting-cell of Eugenia.
+E - zoospore.
+F - zoospore.
+G - zoospore.
+H - zoospore.
+I - zoospore.
+J - zoospore.
+K - zoospore.
+L - zoospore.
+M - zoospore.
+N - zoospore.
+O - zoospore.
+P - zoospore.
+Q - zoospore.
+R - zoospore.
+S - zoospore.
+T - zoospore.
+U - zoospore.
+V - zoospore.
+W - zoospore.
+X - zoospore.
+Y - zoospore.
+Z - zoospore.
+AA - zoospore.
+BB - zoospore.
+CC - zoospore.
+DD - zoospore.
+EE - zoospore.
+FF - zoospore.
+GG - zoospore.
+HH - zoospore.
+II - zoospore.
+JJ - zoospore.
+KK - zoospore.
+LL - zoospore.
+MM - zoospore.
+NN - zoospore.
+OO - zoospore.
+PP - zoospore.
+QQ - zoospore.
+RR - zoospore.
+SS - zoospore.
+TT - zoospore.
+UU - zoospore.
+VV - zoospore.
+WW - zoospore.
+XX - zoospore.
+YY - zoospore.
+ZZ - zoospore.
+AAAAA - zoospore.
+BBBBB - zoospore.
+CCCCC - zoospore.
+DDDDD - zoospore.
+EEEEEE - zoospore.
+FFFFF - zoospore.
+GGGGG - zoospore.
+HHHHH - zoospore.
+IIIII - zoospore.
+JJJJJ - zoospore.
+KKKKK - zoospore.
+LLLLL - zoospore.
+MMMMM - zoospore.
+NNNNN - zoospore.
+OOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOOONNNOO ON N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O N NO O
+
+Fig. 117. — A, Chytridium cella, zooesporangium, sp., attached to the epidermis of Erodium cicutarium. B, Zoosporangium of *Chytridium cella*. C-E. Polyphaga Eugeniae. C, infecting zooesporangium attached to a resting-cell of Eugenia. a (x 20). D, zooesporangium (x 30). E, zooesporangium (x 60). F, after Zorz. G-E. after Nowakowski; F, after Nowakowski.
+
+Order II. Saprolegnines (Humphrey, 19)
+
+The most important family of the Saprolegnines is the Saprolegninae, or Wasmulidae. These are aquatic, much resembling in appearance the *Saprolegnia* of Van Tieghem, but they do not belong to the genus *Saprolegnia* (Fig. 118), which occur as saprophytes upon the bodies of dead insects and crustacea. One species, *S. ferris*, is a very destructive parasite, attacking the eggs and young of fishes, which are often killed in great numbers.
+
+The plant consists of delicate branching hyphae which send roots into the body of the animal upon which it is growing. The proplasm, which lines the cell-wall, contains many small nuclei, and often shows active streaming movement. In some cases there are chromatophores, there is a strong resemblance to the filaments of *Van tieghemia.*
+
+Reproduction.—The plants multiply rapidly by the formation of zooesporangia, which are formed in terminal club-shaped sporangia (b-d), much like those of
+
+Watermark
+
+154
+BOTANY
+
+Vancheria. The zoospores are produced in great numbers, by the division of the protoplasm of the spermatium into as many parts as there are nuclei present.
+In Saprolegnia they escape from a terminal pore, with two terminal cilia. They usually become encysted, and in some cases become as bean-shaped zoospores with two lateral cilia. These, when mature, send out a germ-tube and produce a new plant. In other genera (e.g., Achlya, Aphanomyces), the zoospore becomes cysted immediately upon escaping from the sporangium (Fig. 118, D). In Dictyostelium, which is divisible into two parts, one of each of which a zoospore is produced.
+
+If the sporangium is empty, a new one is formed, either by the end of the old one dividing through the empty sporangium (Fig. 118, D), or by the growth of its base and forming a new sporangium on the side of the old one. This process may be repeated several times.
+
+Sexual Reproduction.--Oogonia, globular in form, within the oogonium one or several egg-cells are formed (Fig. 119). The antheridium is sessile or attached to the wall of the oogonium. In S. Aggregata, the antheridium develops from the same branch as the oogonium. The antheridium is globular in form, and there is a stalk-like canal, formed in connection with each antheridium. The antheridium is closely applied to the wall of the oogonium, into which it sends a tube, which comes into contact with the egg-cell. The spermatozoa pass through this tube from the fertilizing tube, and fuse with the single nucleus in the egg-cell. In most species examined, however, it has been found that although the fertilizing tubes are present they are not functional because they are formed without fertilization. Still other genera (e.g. S. ferax) seldom or never produce antheridia.
+
+The ripe spores, after a period of rest, germinate by sending out a germ-tube which penetrates the nutritive body.
+
+Related to the Water-moulds is the genus Pythium, some species of which are very destructive parasites. One of these, P. De Baryana
+
+![]() A diagram showing a zoospore (A) emerging from a sporangium (B). The zoospore has two lateral cilia and is shown in various stages of movement.
+![]() B Diagram showing a sporangium (B) with two terminal pores and a germ-tube (C) emerging from one of them.
+![]() D Diagram showing a zoospore (D) emerging from a sporangium (E) with two lateral cilia.
+![]() F Diagram showing a cysted zoospore (F).
+![]() G Diagram showing a cysted zoospore (G).
+
+Fig. 118.--A-D, Saprolegnia ferax. A, dead fly covered with Saprolegnia; B, development of zoospores; C, zoospore; D, in D, a new sporangium formed within an empty one. E, Achlya ep., sporangium developing below the empty one (x 375). F, Achlya ep., zoospore; G, Achlya ep., zoospore (x 475). (F., G., after HUMBERT.)
+
+THE FUNGI
+166
+
+num, is the cause of the disease of young seedlings called "damping-off," the Fungus attacking the plant close to the ground, and causing the stem to rot off. The representative of this genus is much like that of the true Water-moulds.
+
+*Myxobolus*, *Simul- ilar in many respects to the Water-moulds, are a number of curious aquatic Fungi, which have been especially studied by Professor Roland Thaxter (22). One of these, *Myrioblepharis*, is a large multiciliate zoospore like those of Vaucheria. *Monoblepharis* (Fig. 120, A, B) has unicillate zoo- spores, but its infection is effected by motile sperma- zooids, as in the Chloro- phyceae.
+
+Order III.
+Peronosporine
+
+This very characteristic order includes a number of very destructive parasitic Fungi, causing some of the most serious diseases of plants. The Fungus attacks within the tissues of the host plant, occupying the spaces between the cells into which suckers (Hantoria) are sent, by which the parasite absorbs the contents of the cells.
+
+*Albugo Candida*. One of the best known of the Peronosporine is the "Albugo Candida," which attacks the Shep- herd's-purse (Capella) and other Cruciferae, where its growth causes great deformation of the host, the flowers and young fruits being especially affected (Fig. 121). The common name is derived from the white or yellowish appearance of the lesions found below the epidermis of the host. The epidermis is finally broken through and the masses of spores set free. In the Eastern States, a common species is *A. biti*, which grows upon the Pigweed (*Am- monia op*) and killed plants and *A. portulaca*, upon the Purslane (*Portulaca oleracea*).
+
+![]()
+A: A diagram showing a section of a plant with a lesion caused by Albugo Candida.
+B: Another diagram showing a section of a plant with a lesion caused by Albugo Candida.
+C: A diagram showing a section of a plant with a lesion caused by Albugo Candida.
+D: A diagram showing a section of a plant with a lesion caused by Albugo Candida.
+II: A diagram showing a section of a plant with a lesion caused by Albugo Candida.
+III: A diagram showing a section of a plant with a lesion caused by Albugo Candida.
+I: A diagram showing a section of a plant with a lesion caused by Albugo Candida.
+
+Fig. 119. - *A*. *Euphorbia amercianum*, fertilization of the stigma by antheridium ; b (x300). (After Thaw.) *C*. Spermogonium (x300). *D*. Antheridium (x300); the oospore, d, develops without fertilization (x300); the oospore, d', develops without fertilization (x300).
+II: A diagram showing a section of a plant with a lesion caused by Albugo Candida.
+III: A diagram showing a section of a plant with a lesion caused by Albugo Candida.
+I: A diagram showing a section of a plant with a lesion caused by Albugo Candida.
+
+156
+BOTANY
+
+The vegetative portion of the Fungus consists of irregular, thick-walled, unil-
+laid hyphae, which follow closely the intercellular spaces in the stem and leaves. The mycelium is very dense, and the cells are often so crowded that they become very irregular and much branched, their extremities forming close tufts of short branches. The sporangia are produced on the tips of these branches, and are developed, are little globular bodies connected with the hypha by a slender neck (Fig. 121, D). The protopodium of the hypha is multinucleate.
+
+Basidiospores. — The spores are formed in succession from the short terminal branches of the hyphae. These conidial branches are known as "basidia." The end of the basidium becomes somewhat enlarged, and slightly curved, and a long neck is formed at its base (Fig. 121, E). This process is repeated until a chain of oval spores is produced, the lowest one being the last formed. In the young conidium the basal wall is thin, and most of this thickened wall becomes later absorbed, leaving only a narrow neck between the conidia, which are then very easily broken apart. With the growth of the conidial mass, the epidermis of the host is finally ruptured, and the spores are thus set free.
+
+Germination. — Each conidium (Fig. 121, F) is an oval cell containing several nuclei. The nuclei divide into two parts each, and each part consists of each conidium dividing into as many parts as there are nuclei, and escaping from the conidium (zoosporangium) very much like the zoospores of Saprolagus. This zoospore swims about in water for some time, during which short period of activity they come to rest, and send out a germ-tube which penetrates the tissues of the young seedling plant or the very young axillary bud of the older one.
+
+![]() A diagram showing a series of stages in the development of a basidium and basidiospores.
+
+**Fig. 121.** — A, B. Monoblastophora insignis; op., oogonium; f., arithemithor; C. Myro-
+biophora paradoxa, development of the multistallate zoospore; op., D. E. Rhiz-
+palium americanaeum; zoosporangium ($\times$ 300); in E, the biciliate zoospore;
+F are zoospores swimming in water.
+
+![]() A diagram showing a series of stages in the germination of a basidium and basidiospores.
+
+THE FUNGI
+157
+
+In the Mildews of the genera Peronospora, Plasmopara, etc., the conidia are formed singly at the ends of branching conidiophores which branch three times and form a delicate downy coating upon the affected parts (Fig. 121, I).
+
+Sex-organ.--A thallus is produced by the growth of the hyphae, the perithecium being formed by the fusion of two such thalli. The former is a globular cell, with a single nucleus, surrounded by a thin wall. As it approaches maturity, there is found a single large egg-cell, surrounded by a nearly transparent layer of cytoplasm in which are numerous nuclei. In
+
+![]()
+A: A normal capsule of Capsidula, slightly enlarged.
+B: Capsule hypertrophied by the growth of Allospora conidios.
+C: Leaf of Amaranthus with pycnidia.
+D: Pycnidium of Dactylis glomerata.
+E: Conidiophore of A. candida (× 250).
+F: Germinating conidium of A. candida.
+G: Conidium of A. candida.
+H: Germinating conidium of A. candida.
+I: Conidiophore of Plasmopara viticola (× 150).
+J: A candida the egg-cell contains but a single nucleus, in J. hirti there are many.
+
+
+Fig. 121. --A, normal capsule of Capsidula, slightly enlarged. B, capsule hypertrophied by the growth of Allospora conidios. C, leaf of Amaranthus with pycnidia. D, pycnidium of Dactylis glomerata. E, conidiophore of A. candida (× 250). F, Germinating conidium of A. candida. G, conidium of A. candida. H, germinating conidium. I, conidiophore of Plasmopara viticola (× 150).
+
+The antheridium is irregular in shape and contains several nuclei. It sends a tube through which the egg-cell passes to the antheridial cavity where it is discharged. When the egg contains but one nucleus, a single antheridal nucleus fuses with it; when it contains two nuclei, there is a fusion of each egg-nucleus with an antheridal one.
+
+The egg now develops a wall and becomes a resting-spore (Fig. 121, D), about which a thick wall is formed. This resting-spore is destroyed by decay; it principally by the activity of the nucleated protoplasm in which the young spore is imbedded.
+
+The resting-spores are not set free until the tissues of the host decay. They germinate either by forming zoospores, or by developing a germ-tube at once.
+
+The following table gives some data regarding the life-history of these fungi:
+
+| Species | Habitat | Spores | Conidia |
+|---------|---------|--------|---------|
+| Peronospora tabacina | Tobacco | Sporangia | Conidia |
+| Plasmopara viticola | Grape | Conidia | Conidia |
+| Allospora candida | Tobacco | Conidia | Conidia |
+
+Note that all these fungi produce conidia as their spores.
+
+The following table gives some data regarding the life-history of these fungi:
+
+| Species | Habitat | Spores | Conidia |
+|---------|---------|--------|---------|
+| Peronospora tabacina | Tobacco | Sporangia | Conidia |
+| Plasmopara viticola | Grape | Conidia | Conidia |
+| Allospora candida | Tobacco | Conidia | Conidia |
+
+Note that all these fungi produce conidia as their spores.
+
+The following table gives some data regarding the life-history of these fungi:
+
+| Species | Habitat | Spores | Conidia |
+|---------|---------|--------|---------|
+| Peronospora tabacina | Tobacco | Sporangia | Conidia |
+| Plasmopara viticola | Grape | Conidia | Conidia |
+| Allospora candida | Tobacco | Conidia | Conidia |
+
+Note that all these fungi produce conidia as their spores.
+
+The following table gives some data regarding the life-history of these fungi:
+
+| Species | Habitat | Spores | Conidia |
+|---------|---------|--------|---------|
+| Peronospora tabacina | Tobacco | Sporangia | Conidia |
+| Plasmopara viticola | Grape | Conidia | Conidia |
+| Allospora candida | Tobacco | Conidia | Conidia |
+
+Note that all these fungi produce conidia as their spores.
+
+The following table gives some data regarding the life-history of these fungi:
+
+| Species | Habitat | Spores | Conidia |
+|---------|---------|--------|---------|
+| Peronospora tabacina | Tobacco | Sporangia | Conidia |
+| Plasmopara viticola | Grape | Conidia | Conidia |
+| Allospora candida | Tobacco | Conidia | Conidia |
+
+Note that all these fungi produce conidia as their spores.
+
+The following table gives some data regarding the life-history of these fungi:
+
+| Species | Habitat | Spores | Conidia |
+|---------|---------|--------|---------|
+| Peronospora tabacina | Tobacco | Sporangia | Conidia |
+| Plasmopara viticola | Grape | Conidia | Conidia |
+| Allospora candida | Tobacco | Conidia | Conidia |
+
+Note that all these fungi produce conidia as their spores.
+
+The following table gives some data regarding the life-history of these fungi:
+
+| Species | Habitat | Spores | Conidia |
+|---------|---------|--------|---------|
+| Peronospora tabacina | Tobacco | Sporangia | Conidia |
+| Plasmopara viticola | Grape | Conidia | Conidia |
+| Allospora candida | Tobacco | Conidia | Conidia |
+
+Note that all these fungi produce conidia as their spores.
+
+The following table gives some data regarding the life-history of these fungi:
+
+| Species | Habitat | Spores | Conidia |
+|---------|---------|--------|---------|
+| Peronospora tabacina | Tobacco | Sporangia | Conidia |
+| Plasmopara viticola | Grape | Conidia | Conidia |
+| Allospora candida | Tobacco | Conidia | Conidia |
+
+Note that all these fungi produce conidia as their spores.
+
+The following table gives some data regarding the life-history of these fungi:
+
+| Species | Habitat | Spores | Conidia |
+|---------|---------|--------|---------|
+| Peronospora tabacina | Tobacco | Sporangia | Conidia |
+| Plasmopara viticola | Grape | Conidia | Conidia |
+| Allospora candida | Tobacco | Conidia |
+
+Note that all these fungi produce conidia as their spores.
+
+The following table gives some data regarding the life-history of these fungi:
+
+
+| Species | Habitat | Spores | Conidia |
+| Peronospora tabacina | Tobacco | Sporangia | Conidia |
+| Plasmopara viticola | Grape | Conidia | Conidia |
+| Allospora candida | Tobacco | Conidia | Conidia |
+
+
+Note that all these fungi produce conidia as their spores.
+
+The following table gives some data regarding the life-history of these fungi:
+
+
+| Species | Habitat | Spores | Conidia |
+| Peronospora tabacina | Tobacco | Sporangia | Conidia |
+| Plasmopara viticola | Grape | Conidia | Conidia |
+| Allospora candida | Tobacco | Conidia | Conidia |
+
+
+Note that all these fungi produce conidia as their spores.
+
+The following table gives some data regarding the life-history of these fungi:
+
+
+| Species | Habitat | Spores | Condia | |
|---|
+| Peronospora tabacina | Tobacco | Sporangia | Condia | |
|---|
+| Plasmopara viticola | Grape | Condia | Condia | |
|---|
+| Allospora candida | Tobacco | Condia | Condia | |
|---|
+
+
+Note that all these fungi produce conidia as their spores.
+
+The following table gives some data regarding the life-history of these fungi:
+
+
+| Species | Habitat | Spores | Conida | |
|---|
+| Peronospora tabacina | Tobacco | Sporangia | Conida | |
|---|
+| Plasmopara viticola | Grape | Conida | Conida | |
|---|
+| Allospora candida | Tobacco | Conida | Conida | |
|---|
+
+
+Note that all these fungi produce conida as their spores.
+
+The following table gives some data regarding the life-history of these fungi:
+
+
+| Species | Habitat | Spores | Conida | |
|---|
+| Peronospora tabacina | Tobacco | Sporangia | Conida | |
|---|
+| Plasmopara viticola | Grape | Conida | Conida | |
|---|
+| Allospora candida | Tobacco | Conida | Conida | |
|---|
+
+
+Note that all these fungi produce conida as their spores.
+
+The following table gives some data regarding the life-history of these fungi:
+
+
+| Species | Habitat | Spores | Conida | |
|---|
+| Peronospora tabacina | Tobacco | Sporangia | Conida | |
|---|
+| Plasmopara viticola | Grape | Conida | Conida | |
|---|
+| Allospora candida | Tobacco | Conida | Conida | |
|---|
+
+
+Note that all these fungi produce conida as their spores.
+
+The following table gives some data regarding the life-history of these fungi:
+
+
+| Species | Habitat | Spores | Conida/th colspan="3"> |
|---|
+Peronospora tabacina
P.
V.
A. | Tobacco
Grape
Tobacco
A. | Sporangia
Sporangia
Sporangia
Sporangia
C.
E.
F.
G.
H.
I.
J. | Conida
C.
E.
F.
G.
H.
I.
J. |
|---|
+Sporangia
Sporangia
Sporangia
Sporangia
C.
E.
F.
G.
H.
I.
J. |
|---|
+Sporangia
Sporangia
Sporangia
Sporangia
C.
E.
F.
G.
H.
I.
J. |
|---|
+Sporangia
Sporangia
Sporangia
Sporangia
C.
E.
F.
G.
H.
I.
J. |
|---|
+Sporangia
Sporangia
Sporangia
Sporangia
C.
E.
F.
G.
H.
I.
J. |
|---|
+Sporangia
Sporangia
Sporangia
Sporangia
C.
E.
F.
G.
H.
I.
J. |
|---|
+Sporangia
Sporangia
Sporangia
Sporangia
C.
E.
F.
G.
H.
I.
J. |
|---|
+Sporangia
Sporangia
Sporangia
Sporangia
C.
E.
F.
G.
H.
I.
J. |
|---|
+Sporangia
Sporangia
Sporangia
Sporangia
C.
E.
F.
G.
H.
I.
J. |
|---|
+Sporangia
Sporangia
Sporangia
Sporangia
C.
E.
F.
G.
H.
I.
J. |
|---|
+Sporangia
Sporangia
Sporangia
Sporangia
C.
E.
F.
G.
H.
I.
J. |
|---|
+Sporangia
Sporangia
Sporangia
Sporangia
C..![]() A: A normal capsule of Capsidula, slightly enlarged.
+B: Capsule hypertrophied by the growth of Allospora conidios.
+C: Leaf of Amaranthus with pycnidia.
+D: Pycnidium of Dactylis glomerata.
+E: Germinating conidium of A. candida (× 250).
+F: Germinating conidium of A. candida.
+G: Germinating conidium of A. candida.
+H: Germinating conidium of A. candida.
+I: Germinating conidium of A. candida.
+J: A candida the egg-cell contains but a single nucleus, in J. hirti there are many.
+E: Germinating conidium of A. candida.
+F: Germinating conidium of A. candida.
+G: Germinating conidium of A. candida.
+H: Germinating conidium of A. candida.
+I: Germinating conidium of A. candida.
+J: A candida the egg-cell contains but a single nucleus, in J. hirti there are many.
+E: Germinating conidium of A. candida.
+F: Germinating conidium of A. candida.
+G: Germinating conidium of A. candida.
+H: Germinating conidium of A. candida.
+I: Germinating conidium of A. candida.
+J: A candida the egg-cell contains but a single nucleus, in J. hirti there are many.
+E: Germinating conidium of A. candida.
+F: Germinating conidium of A. candida.
+G: Germinating conidium of A. candida.
+H: Germinating conidium of A. candida.
+I: Germinating conidium of A. candida.
+J: A candida the egg-cell contains but a single nucleus, in J. hirti there are many.
+E: Germinating conidium of A. candida.
+F: Germinating conidium of A. candida.
+G: Germinating conidium of A. candida.
+H: Germinating conidium of A. candida.
+I: Germinating conidium of A. candida.
+J: A candida the egg-cell contains but a single nucleus, in J. hirti there are many.
+E: Germinating conidium of A. candida.
+F: Germinating conidium of A. candida.
+G: Germinating conidium of A. candida.
+H: Germinating conidium of A. candida.
+I: Germinating conidium of A. candida.
+J: A candida the egg-cell contains but a single nucleus, in J. hirti there are many.
+E: Germinating conidium of A. candida.
+F: Germinating conidium of A. candida.
+G: Germinating conidium of A. candida.
+H: Germinating conidium of A. candida.
+I: Germinating conidium of A. candida.
+J: A candida the egg-cell contains but a single nucleus, in J. hirti there are many.A normal capsule
+of Capsidula, slightly enlarged
+B Capsule hypertrophied by
+the growth
+of Allospora
+conidi
+C Leaf
+of Amaranthus
+with pycnid
+D Pycnid
+E Pycnidi
+F Pycnidi
+G Pycnidi
+H Pycnidi
+I Pycnidi
+J Pycnidi
+A Candidula
+B Candidula
+C Candidula
+D Candidula
+E Candidula
+F Candidula
+G Candidula
+H Candidula
+I Candidula
+J Candidula
+
+Note that all these fungi produce
+conida as their spores.
+
+The following table gives some data regarding the life-history
+
+
+
+
+
+THE FUNGI
+
+In the Mildews
+
+of genera Peronospora,
+
+Plasmopara,
+
+etc.,
+
+the
+
+conidi
+
+are formed singly at
+
+the ends
+
+of branching
+
+conidiophor
+
+which branch three times and form
+
+delicate downy coating upon affected parts (Fig.
+
+121,
+
+I).
+
+Sex-organ.--A thallus is produced by
+
+the growth
+
+of Allospora
+
+conidi,
+
+etc.,
+
+and forms
+
+from separate branches.
+
+The former is a globular cell,
+
+with a single nucleus,
+
+surrounded by a thin wall.
+
+As it approaches maturity,
+
+there is found a single large egg-cell,
+
+surrounded by a nearly transparent layer
+
+of cytoplasm in which are numerous nuclei.
+
+A normal capsule
+
+of Capsidula,
+
+slightly enlarged.
+
+Capsule hypertrophied by
+
+the growth
+
+of Allospora
+
+conidi,
+
+etc.,
+
+and forms from separate branches.
+
+The former is a globular cell,
+
+with a single nucleus,
+
+surrounded by a thin wall.
+
+As it approaches maturity,
+
+there is found a single large egg-cell,
+
+surrounded by a nearly transparent layer
+
+of cytoplasm in which are numerous nuclei.
+
+A normal capsule
+
+of Capsidula,
+
+slightly enlarged.
+
+Capsule hypertrophied by
+
+the growth
+
+of Allospora
+
+conidi,
+
+etc.,
+
+and forms from separate branches.
+
+The former is a globular cell,
+
+with a single nucleus,
+
+surrounded by a thin wall.
+
+As it approaches maturity,
+
+there is found a single large egg-cell,
+
+surrounded by a nearly transparent layer
+
+of cytoplasm in which are numerous nuclei.
+
+A normal capsule
+
+of Capsidula,
+
+slightly enlarged.
+
+Capsule hypertrophied by
+
+the growth
+
+of Allospora
+
+conidi,
+
+etc.,
+
+and forms from separate branches.
+
+The former is a globular cell,
+
+with a single nucleus,
+
+surrounded by a thin wall.
+
+As it approaches maturity,
+
+there is found a single large egg-cell,
+
+surrounded by a nearly transparent layer
+
+of cytoplasm in which are numerous nuclei.
+
+A normal capsule
+
+of Capsidula,
+
+slightly enlarged.
+
+Capsule hypertrophied by
+
+the growth
+
+of Allospora
+
+conidi,
+
+etc.,
+
+and forms from separate branches.
+
+The former is a globular cell,
+
+with a single nucleus,
+
+surrounded by a thin wall.
+
+As it approaches maturity,
+
+there is found a single large egg-cell,
+
+surrounded by a nearly transparent layer
+
+of cytoplasm in which are numerous nuclei.
+
+A normal capsule
+
+of Capsidula,
+
+slightly enlarged.
+
+Capsule hypertrophied by
+
+the growth
+
+of Allospora
+
+conidi,
+
+etc.,
+
+and forms from separate branches.
+
+The former is a globular cell,
+
+with a single nucleus,
+
+surrounded by a thin wall.
+
+As it approaches maturity,
+
+there is found a single large egg-cell,
+
+surrounded by a nearly transparent layer
+
+of cytoplasm in which are numerous nuclei.
+
+A normal capsule
+
+of Capsidula,
+
+slightly enlarged.
+
+Capsule hypertrophied by
+
+the growth
+
+of Allospora
+
+conidi,
+
+etc.,
+
+and forms from separate branches.
+
+The former is a globular cell,
+
+with a single nucleus,
+
+surrounded by a thin wall.
+
+As it approaches maturity,
+
+there is found a single large egg-cell,
+
+surrounded by a nearly transparent layer
+
+of cytoplasm in which are numerous nuclei.
+
+A normal capsule
+
+of Capsidula,
+
+slightly enlarged.
+
+Capsule hypertrophied by
+
+the growth
+
+of Allospora
+
+conidi,
+
+etc.,
+
+and forms from separate branches.
+
+The former is a globular cell,
+
+with a single nucleus,
+
+surrounded by a thin wall.
+
+As it approaches maturity,
+
+there is found a single large egg-cell,
+
+surrounded by a nearly transparent layer
+
+of cytoplasm in which are numerous nuclei.
+
+A normal capsule
+
+of Capsidula,
+
+slightly enlarged.
+
+Capsule hypertrophied by
+
+the growth
+
+of Allospora
+
+conidi,
+
+etc.,
+
+and forms from separate branches.
+
+The former is a globular cell,
+
+with a single nucleus,
+
+surrounded by a thin wall.
+
+As it approaches maturity,
+
+there is found a single large egg-cell,
+
+surrounded by a nearly transparent layer
+
+of cytoplasm in which are numerous nuclei.
+
+A normal capsule
+
+of Capsidula,
+
+slightly enlarged.
+
+Capsule hypertrophied by
+
+the growth
+
+of Allospora
+
+conidi,
+
+etc.,
+
+and forms from separate branches.
+
+The former is a globular cell,
+
+with a single nucleus,
+
+surrounded by a thin wall.
+
+As it approaches maturity,
+
+there is found a single large egg-cell,
+
+surrounded by a nearly transparent layer
+
+of cytoplasm in which are numerous nuclei.
+
+A normal capsule
+
+of Capsidula,
+
+slightly enlarged.
+
+Capsule hypertrophied by
+
+the growth
+
+of Allospora
+
+conidi，
+
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc., and forms from separate branches,
+et al., etc.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et al.,
+et
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+al...
+
+Note that all these fun...
+
+```
+
+158
+BOTANY
+
+Among the common Peronosporineae may be mentioned *Phytophthora infestans*, the Potato-fungus; *Plasmopara viticola*, the Vine-millet; *Peronospora Schleideni*, the Onion-mould, as well as many other destructive species.
+
+**Fig. 123.** — A, C, *Dispor conidia*. A, young sexual organs (× 40). B, oogonium, with antheridium and antheridial spores (× 400). C, mature oogonium containing a fertilised egg surrounded by a membrane, outside of which lies the zone of nucleated periplasm (× 325). D, A, bitt, oogonium with ripe spore (× 300). (A, C, after Watson.)
+
+SUBCLASS II. ZYGOMYCETES
+
+The Zygomycetes, of which the Black-moulds are the most familiar examples, differ from the other Phycomycetes in not producing motile reproductive cells. Where a sexual reproduction is known, it consists in the fusion of two similar cells by a process of conjugation not involving any nuclear division. But this superficial resemblance indicates any relationship between the two groups.
+
+There are two orders, Mucorineae and Entomophoriniae, the former being mostly saprophytes, the latter parasites.
+
+ORDER I. MUCORINEAE
+
+The order Mucorineae includes several families, mostly saprophytes but some parasitic, known popularly as Black-moulds, as the spores and fruiting hyphae are usually black. As a type of the order
+
+THE FUNGI
+160
+
+we may select the very common *Mucor stolosifer* (*Rhizopus nigricans*), belonging to the family Mucoraceae (Figs. 123, 124). This common mould is a saprophyte, growing on decaying vegetable matter, and articles of food, and appears spontaneously upon bread exposed to a moist warm atmosphere. The hyphae are thin-walled, colorless at first, but turning dark with age. Slender rootlets are sent down into the nutrient substrate, and these rootlets give rise to the sporangiophores, producing bright ones (sporangiophores) and horizontal slender runners, or stolons, which strike root, and produce a new crop of sporangiophores. The protoplasmic contents are quite colorless,
+
+![]()
+A - ep
+B - r
+C - D
+D - E
+
+
+Fig. 123. — *Mucor stolosifer*. A, sporangiophores connected by stolon, and sending down roots, r, slightly enlarged. B, young sporangiophores, more highly magnified. C-E, diagram of sporangium (123).
+
+
+densely granular in the growing branches, and often containing con-
+spicuous spores. Sometimes, as in the Water-moulds, streaming
+movements are visible.
+
+**Sporangium.** — Each sporangiophore becomes enlarged at the end, which finally is cut off as a globular sporangium. The partition wall is convex, and grows into the outer wall of the sporangium. The protoplasm is contained between it and the outer sporangium-wall. The protoplasm within this space becomes divided by deep clefts into a number of parts which divide further until a large number of spores (sporangia) are produced. Each of these becomes surrounded by a thick wall, which assumes a smoky black colour, thus being also
+
+![]()
+A - ep
+B - r
+C - D
+D - E
+
+
+100
+BOTANY
+
+the case with the wall of the stalk of the sporangium. At maturity the outer mem-
+brane of the sporangium, which in many Monocera contains minute calcareous bodies, becomes mucilaginous, and on being wet, dissects and sets free the ripe spores, which are then liberated by rupture of the distended bulb below. With proper manure they grow with great rapidity, and soon develop a new mycelium.
+
+*Pileobolus.* — In the genus Pileobolus (Fig. 125, B, C), which grows abundantly upon stable manure, the stout sporangiophores are much distended just below the sporangium. When the latter is ripe, a ring-shaped swelling appears at the base of the bulb. The spore formation in the distended bulb below the sporangium is suddenly liberated with such force as to project the sporangium to a long distance. Where
+
+![]() A B C D E
+
+**Fig. 125.** — *Mucor stolonifer.* Development of zygospora. *A-B*, × 225.
+
+the plants are grown under a mulipe, its inner surface soon appears dotted with the adherent sporangia thrown off in this way.
+
+In other genera, e.g. Chattochadium and Syncephala, the spores are conidia, somewhat like those of Allbuco. They may be borne singly or in chains (Fig. 125, A).
+
+Sexual Reproduction — Zygospora, formed from the union of two cells borne at the end of short branches, are found in many of the Monocera, but as a rule they are not abundant. In *Chattochadium* (Fig. 124) the process begins by the sending out of short branches from neighboring hy-
+pae, which become enlarged into a large cell containing a large protop-
+lasma in these branches, which becomes much enlarged, is very dense and granular, and from the end of each cell is cut off which forms one of the
+
+THE FUNGI
+15
+
+gametangia. The cell-wall separating the two cells now is absorbed and their con-
+tent is lost. Whether the nuclei fuse in pairs, as in *Albugo* *blit*, is not known,
+but it is most likely to be so.
+
+The zygote increases greatly in size, as the contents of the protoplasm in the hemisphere which the gametes were formed. It be-
+comes vacuolate, with dense granular contents, and the wall becomes thickened and opaque. The ripe zygote is hypo-
+cytic between the mem-
+branes, the out-
+growth of the original membrane of the conjugating cells.
+
+In *Pityococcus* *Freseniana* (*x 300*). (After
+Baker.) A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z.
+(A, b; x 300; w, drops of water; sp., sarcinum.)
+
+The zygospore is formed as an outgrowth at the point of juncture of the gametes,
+and not by their direct fusion. In Mortierella the zygospore is sur-
+rounded by a dense growth of hyphae, which completely conceals it.
+
+Order II. Entomophthorineae (Thaxter, 20)
+
+The Entomophthorineae are Fungi parasitic upon insects of various
+kinds, which are killed by their attacks (Fig. 126). The commonest form is *Empusa musca*, which attacks the common house-fly. The infested insect is first attacked on its back by a small spot,
+to window-pane, and surrounded by a whitish halo of the Fungus-
+spores. The germinating spores penetrate the body of the insect,
+probably through the thin membrane between the rings of the body
+through which they pass into the alimentary canal. Here they grow
+rapidly, forming, by budding, a great number of short hyphal
+joints, which sometimes become dormant for a longer or shorter period.
+After these have completely exhausted the nutritive matter from the
+whiskers and feet of the insect, new buds are produced. These bud-
+ture are provided each by a body developing one or more basidia
+which break through the thin places in the integument of the insect.
+Upon emerging, each basidium has cut off from its extremity a
+single conidium, or perhaps more exactly a sporangium containing a
+single spore which completely fills it. These conidia are shot off,
+
+![]() A diagram showing a zygote (A) with a dense granular content and an opaque wall. The zygote is surrounded by a dense growth of hyphae (B), which completely conceals it.
+![]() C shows a zygospore (sp.) with a dense granular content and an opaque wall. The zygospore is surrounded by a dense growth of hyphae (sp.), which completely conceals it.
+
+168
+BOTANY
+
+much as in the case of Pilobolus, and it is these discharged conidia which form the halo about the dead fly.
+**Zygosporae.** Zygosporae, quite like those of the Mucorineae, have been found in a few species of Ascomycetose (Fig. 125, C), and in some forms similar spores are developed without fertilization.
+
+SERIES II. EUMYCETES (TRUE FUNGI)
+
+Very much the greater part of the Fungi belong to the Eumycetes, or, as they are sometimes called, the Mycomycetes. The Eumycetes are so modified that they show very little trace of any relationship.
+
+![]() A butterfly (Colias) attached by Engus sp. to a leaf.
+![]() B
+![]() C
+
+Fig. 125.—A, Butterfly (Colias), attached by Engus sp. to a leaf. B, E. musae, group of conidiophores (× 230). C, zygospore-formation in E. squarrosa (× 280), showing also the hyphae.
+
+with the green plants, and their classification presents many difficulties. With a few exceptions they readily fall into two great divisions or classes, which are not evidently related to each other. These are the Ascomycetes or Sac-fungi, and the Basidiomycetes, which include the Toadstools, Puffballs, Rusts, and many of the most familiar of the true Fungi. The latter class has been sometimes added, but this is a somewhat artificial group, as some of its members are related to the Ascomycetes, others to the Basidiomycetes.
+
+**Mycelium.** — The mycelium in the Eumycetes is usually composed of hyphae with cross-walls or septa at regular intervals, and formed
+
+THE FUNGI 163
+
+in succession back of the apex of the hyphae, which thus shows a definite apical growth.
+
+**Reproduction.** — Spores of various kinds are produced, sometimes borne directly upon the mycelium, but more commonly confined to special structures, the spore-fruit or sporocarp, which may reach a large size. The production of spores by fungi has been demonstrated in a small number of the Eumycetes, but in most of them no trace of any form of sexuality has been found, although it is quite likely that it exists in a larger number than is at present supposed.
+
+Biology. — Both sexual and asexual reproduction are common among the Eumycetes. Some forms, like the Rusts and Smuts, are extremely destructive parasites, others, like the Mushrooms, Puffballs, etc., are saprophytes, usually living upon dead vegetable matter. In these forms the mycelium is buried in the nutritive substratum, only the large sporeshells being visible above its surface.
+
+**Class I. ASCOMYCETES**
+
+The Ascomycetes, or Sac-fungi, include the major part of the Fungi and exhibit great variety in structure and habits as well as in their habits. While they may develop several kinds of spores, there are always found the ascospores, which are formed by free-cell formation within sac-like structures known as ascus. In the lowest types, the Hymenomycetes, the number of ascospores in the ascus is large, but in much the greater part it is regularly eight.
+
+**Ascospore-formation.** — The youngascus (Fig. 127), A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z are typical. Ascomyces contain two nuclei lying in the
+
+![]() Fig. 127.—Pyronema confusum. Development of the ascus. (After HARRAN.) A., ascomycous hypha with two nuclei; B., older ascus; the nuclear fusing. C.,ascus with single nucleus derived from the fusions of the two primary nuclei; D., dividing hypha; E., developing ascospores.
+
+nucleus derived from the fusions of the two primary nuclei; D., dividing hypha; E., developing ascospores.
+
+163
+
+164
+BOTANY
+
+granular vacuolated cytoplasm. The two nuclei fuse into a single one, which then undergoes repeated divisions until eight free nuclei are formed. At the poles of the nuclear spindle there is a con-
+spicuous mass of protoplasm, which soon becomes transformed to a well-marked aster which persists after the division is com-
+plete (Fig. 127, E-G). The nucleus develops a beak from which the aster-ribes radiate. The latter next arrange themselves in the form of a wheel about the beak of the nucleus and gradually increase in length, thus finally cutting out a new layer of protoplasm from the cyto-
+plasm, which encloses the nucleus, and thus forms the young spore.
+A firm wall is developed about the spores, which are imbedded in the remaining cytoplasm of the ascus (G).
+
+![]() A, B, C
+
+Fig. 128. — Dipodacous albicus. Development of the ascus. (After LAGERRE.) (300.)
+
+SUBCLASS I. HEMIASCINAE
+
+The Ascomycetes may be divided into two subclasses, the Hemi-
+ascinae, in which the spores are produced in large numbers within
+the ascus, and the Eucacea, where the number of ascospores is, with
+few exceptions, limited to two. The former class includes many num-
+ber, parasites or saprophytes. Their reproduction is for the most
+part non-sexual, but in the peculiar genus Dipodacous (Fig. 128)
+there is a fertilization of an oogonium by fusion with the antheridium,
+and this is followed by a development of a sporangium containing numerous spores. In the genus Protonyces, which is not always placed among the Ascomycetes, the numerous spores formed in the ascii (?) fuse in pairs before germination, much like the gametes of the lower Algae.
+
+—
+
+THE FUNGI 165
+
+SUBCLASS II. EUASCOM
+
+Order I. Protoasciines
+
+The lowest of the Euascom, the Protoasciines, comprise two families, the Saccharomyctecae and the Endomyctecae. The former include the Yeast-fungi, whose relation to the Ascomycetes is somewhat doubtful; the second family comprises a small number of very simple but unmistakable Sac-fungi.
+
+**Yeast-fungi.** — The Saccharomyctecae or Yeast-fungi, unlike the true Fungi, do not develop no mycelium, but consist of isolated oval cells which multiply by budding (Fig. 128), and only exceptionally become elongated into a hypha. The oral vegetative cells contain granular cytoplasm, which may be either vacuolate or more conspicuous vacuoles (Fig. 129). A nucleus is probably present, but it is not readily demonstrated. Under certain conditions, as for example when the cells are cultivated upon slices of carrot or lettuce, they assume a more or less firm (usually) four spore, so that the cell is transformed into a very simple ascus.
+
+Alcoholic Fermentation. — It is from an economic standpoint, however, that the Yeast-fungi are of special interest, as they are the most important agents of alcoholic fermentation. If the cells are placed in a solution of sugar, or a starchy mixture, there soon begins the development of alcohol and carbonic acid gas, with the escape of this latter in the fermenting dough which causes it to rise. The yeast-cells feed upon the starch and sugar, which are attacked by certain peculiar substances (ferments) excreted by the growing yeast-cells. These ferments act upon starch and cellulose, and invertase changes cane-sugar into glucose and fructose, which are available to the yeast-cells for food.
+
+The different species of yeast behave very differently with regard to the fermentation substance, and in many cases vary even the character of the fermentations. This is largely dependent upon the kind of yeast employed; hence the importance of regulating this.
+
+**Endomyctecae.** — The Endomyctecae comprise a small number of forms differing from the Yeasts in having a true mycelium and usually 4-8-spored ascus. In Eremascus the ascus arises from the fer-
+
+![]() A diagram showing a yeast cell undergoing budding.
+A B D n
+
+![]() E shows a yeast cell with a nucleus visible within its cytoplasm.
+E n
+
+![]() C shows a yeast cell with a nucleus visible within its cytoplasm.
+C n
+
+Fig. 128.—Saccharomyces cerevisiae. A, active cell, budding (* 300). B-D, dividing-cells (after Wannier); n, nucleus; E, cell containing vacuole.
+RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RARE BOOKS RASE
+
+106
+BOTANY
+
+tilization of an ascogonium; in Endomycyes and the other genera, the plants are entirely non-sexual.
+
+**Order II. Protodiacinaceae**
+
+The Protodiacinaceae comprise a small number of very simple Ascomycetes, which are mostly parasites upon Flowering Plants.
+
+![]() A
+![]() B
+
+Fig. 130. — A, base of a Fench leaf distorted by *Eusoma deformans*. B, sect. (300).
+
+One of the most familiar is *Eusoma deformans*, which causes the distortions of perch leaves shown in Fig. 130. The *Cult* (Fig. 131) is a small fungus grown between the layers of the cuticle of the epidermal cells of the host, and is composed of many short joints, all of which become ultimately transformed into the seed-wax-like spores, which are produced in great numbers under the leaf. This is thereby very much enlarged and crumpled, and often made bright red in consequence of ripe and form a delicate grey powdery film over the affected parts.
+
+![]() A
+![]() B
+
+**Order III. Helvelliaceae**
+
+In these Fungi the mycelium is well developed, and produces a thallus or thallus-like thallus, borne upon large, characteristic fruiting-bodies, upon parts of which the closely set hyphae form a common layer (Hymenium) consisting of the aeci interspread with sterile filaments, or paraphyses. Of the commonest forms belonging to this order is the Morel (Morchella), whose spore-fruit consists of a stout stalk which is deeply honeycombed with broad pits lined with the
+
+![]() A
+![]() B
+
+Fig. 131. — A, *Helvella incassata*. B, *Morchella* (Natural size.)
+
+THE FUNGI
+167
+
+hymenium. This is one of the best known of the edible Fungi (Fig. 131, B).
+
+Order IV. *Perizineae*
+
+The Perizineae are a large order containing more than three thousand species, among which are a number of conspicuous forms. Among these are the Cup-fungi (Peziza, Ascodonia, etc.). The mycelium is well developed, composed of extensively ramifying hyphae which are usually buried in the nutrient substratum. Most of the genera are saprophytes, growing both upon ani-
+mal and vegetable mat-
+ter. A few of them are parasites, either
+strictly so, as in the
+genus Pyrenopeziza, one
+species of which, *P.
+emergens*, has been found
+upon the Blue-gum (*Eucalyptus globulus*) in California; or they may be parasitic in their earlier stages and complete their development in the dead tissues of the host. This is seen in various species of
+*Seletorinia*.
+
+Reproduction. — A few of the Perizineae produce conidia, but in most of them there are only the ascospores, which are commonly
+
+![]() A group of sexual organs, highly magnified. B, antheridium, A, fusing with the trichogyne, i., C. Asco-
+spores p., spore mother cells from which the ascogenous filaments arise (× about 250). (Somewhat schematic.)
+Fig. 133. — A, B, *Pyronema confluens*. (After HARPER.) A, group of sexual organs, highly magnified. B, antheridium, A, fusing with the trichogyne, i., C. Asco-
+spores p., spore mother cells from which the ascogenous filaments arise (× about 250). (Somewhat schematic.)
+
+A
+B
+C
+
+108
+BOTANY
+
+eight in number, but may be much more numerous; e.g., *Strigocoleus Boudieri* has thirty-two. The setae closely secrete with the paraphyses to form a continuous hymenium lining the interior of the usually cup-shaped, large spore-fruit. These are often very conspicuous and brilliantly colored—yellow, orange, or scarlet.
+
+**Sex-organ.** —The formation of the spore-fruit is usually purely vegetative, but in a few instances, of which the best known is *Pyronema confluens* (Fig. 133), there are indications that sexual reproduction occurs. In this case, a nearly globular oogonium, having a curved tubular outgrowth, the conjugating tube, which is later cut off by a basal wall from the body of the oogonium. The antheridium is a short stalked structure, with a terminal opening into which its contents pass. The basal wall of the conjugating tube next becomes partially absorbed, and allows the contents of the antheridium to pass over into
+
+![]() A diagram showing the formation of a spore-fruit. A shows a section of another fruit, B shows a section of another fruit, C shows a section of another fruit, D shows a section of another fruit.
+
+**Fig. 134.** —A, a Truffle (Tuber aestivum). (Natural size.) B, section of another fruit. T, fruit showing the spongyous region, ap. C1, and of T. rugatum. (All after TULLEAU.)
+
+the body of the oogonium, where each antheridial nucleus fuses with one of those in the oogonium, somewhat as in the compound fertilization in *Algae balti*. Fresh-broken fruits show a network of hyphae between the subhymenial hyphae, and upon these are later formed the sexi. From the hyphae adjacent to the oogonium numerous branches develop which grow in among the mesogenous hyphae, and produce spores which are similar to those produced by other Truffles of its color. The subhymenial tissue and the outer tissues of the fruit also arise from the sterile filaments. The sexi produce eight spores in the manner described.
+
+**Order V. Tuberineae**
+
+**Truffles** —The Tubereuses, or Truffles, live for the most part entirely underground. It is supposed that the mycelium in many of them grows connected with the roots of various trees, forming the so-called Mycorhiza, but the development of the group is imperfectly
+
+THE FUNGI 169
+
+known. The fruits are also borne underground, and in the genuine Truffles are tuberlike bodies which contain numerous canals or channels through which the spores pass. In the Gymnosporangia there are the usual eight ascospores, but in the genuine Truffle (Tuber) (Fig. 134) the number may be reduced to two, or even a single one. The order is poorly represented in America, but in the Pacific States a number of forms have been recorded.
+
+Order VI. Plectascinaceae
+
+The Plectascinaceae are, for the most part, saprophytic Fungi, whose well-developed mycelium may be either buried in the nutritious substratum or is superficial. Some of them, e.g. species of Penicillium, may produce alcoholic fermentation. In many species conidia of characteristic form are developed, in addition to the ascus. The latter in the lowest types, the Gymnosporangia are borne directly on the mycelium, but in most of them club-like fruits, somewhat like those of the Tuberaeae, are produced, and these in a few cases have been shown to result from the artitization of an oogonium.
+
+![]() A
+![]() B
+![]() C
+![]() D
+
+**Aspergillaceae.**
+
+The most familiar members of this order belong to the Aspergillaceae, and are known by their color as Blue or Green Moulds from the color of the conidiospores which are produced by many species. Of these, the common Herbarium-mould (Aspergillus nigerum) and the common Blue- mould (Penicillium glaucum pleuroc.) are well known (Fig. 135). The latter is almost any organic substance.
+
+The most ubiquitous of all Moulds. From the white mycelium there are sent up delicate upright conidiophores, which in Aspergillium develop a bulbous swelling at the apex, while in Penicillium the conidiophore forms several short terminal branches. From the enlarged terminal body, or from the ends of the
+
+![]() E
+![]() F
+![]() G
+![]() H
+
+Fig. 135.—A, *Penicillium glaucum* (× 50). B, *Eurotium herbarum* (× 500). C, sexual organs of *P. crustosum* (× 500). D, *Penicillium crustosum* (× 500). E, *A. niger* (× 800). (C after BARKER.)
+
+170
+BOTANY
+
+branches, small papillae (sterigmata) grow, from each of which is developed a chain of small vesicles, very much as in Albugo.
+
+Sex-organ.- In both Aspergillus and Penicillium the sexual organs (Fig.
+135, C) consist of two nearly similar short filaments, which become closely inter-
+twined, and form a small vesicle (Fig. 135, D). From this there is then formed a mass of sterile hyphae, which completely encloses them and forms the wall of the Perithecium. The spores are produced within the
+subicular body; but before these hyphae are developed, and the small oval ascus
+(Fig. 135, K) is formed in large numbers. The outer cells of the peritheciurn
+form a yellow rim.
+
+![]() A diagram showing the structure of a fungus spore.
+![]() B
+![]() C
+![]() D
+
+![]() E
+![]() F
+![]() G
+![]() H
+
+Fig. 135. - Sphaerothecum castanum. A, conidiophore. B, sexual organs. C, young peritheciurn with sterile hyphae. D, mature perithecium. E, spore; F, ascus; G, ascospore; H, the nucleus of the antheridium has passed into the ascospore. G', ac-
+rogenous filament developed from the fertilized oogonium. (P, Q, after HARPER.)
+
+Order VII. Pyrenomycetes
+
+The Pyrenomycetes, or Black Fungi, comprise over ten thousand species, and include a great variety of both parasitic and saprophytic forms. The mycelium may be composed of delicate, quite distinct
+hyphae, as in the common powdery Mildew, or the vegetative body
+of the Fungus may be composed of closely coherent hyphae, which in sections appear to be solid masses of tissue; but in such cases this
+cohesion is so great; and is combined with such a thickening and
+blackening of the cell-walls, that the cell-structure becomes very
+obscure; and a large, hard, black mass (Stroma) is produced, from
+which later spores are formed.
+
+Reproduction.- The Pyrenomycetes are many of them character-
+ized by a marked polymorphy ; i.e. spores of several kinds are
+
+THE FUNGI
+171
+
+produced, which in some cases have led to confusion in their classification. The formation of the spore-fruit is in some cases preceded by the development of sexual organs and a genuine fertilization, but there is no indication of this in many of them no trace of sexuality remains.
+
+**Periparateles.** — The simplest of the Pteromycetes are the Mildews and their allies, the Mucorales. The best known of these are those belonging to the genus *Sphaerotheca*, one of many common plant-parasites. The Rose-mildew (*Sphaerotheca pannosa*) is perhaps the most familiar. Mildews are superficial parasites, the mycelium forming a delicate web over the surface of the host, into which are sent short hyaline hyphae (Fig. 138). These hyphae send up from the uppermost upright conidiophores, which divide into a series of short aerial hyphae, and then somewhat break off at barrell-shaped conidia. It is these masses of conidia which give the powdery appearance to mildewy growths.
+
+**Sex-organ.** — The sexual organs have been especially studied in *Sphaerotheca* *congelatii* (Fig. 136), which is common upon the Dandelion, and upon a variety of other plants. In this species the number of conidia begins to decline. The oogonium is an oval cell with a single nucleus. From a branch close by, the antheridial branch grows out, bearing a spermatium within its wall.
+
+From a branch close by, the antheridial branch grows out, bearing a spermatium within its wall.
+
+The antheridium is a flask-shaped body, with a narrow neck. The antheridial cell is cut off from its apex, and sends out a slender hypha into which its nucleus passes, the nucleus fusing with that of the oogonium. The two nuclei thus formed fertilize each other, and division occurs. In this manner, the end-cell of which becomes the single ascus found on the surface of the plant (Fig. 137).
+
+The wall of the peritheium is formed from filaments growing from the base of the antheridium, and completely enclosing it. It is not unlike that of Aspergillus.
+
+The outer cells are dark-colored, so that the ripe perithecium appears as black specks scattered over the whole mycelium.
+
+In Erysiphe and other genera the asogenous hypha derived from the oogonium develops several aeci (Fig. 137). From the outer
+
+![]() A B
+![]() A h B
+![]() A h B
+
+Fig. 138. — *Erysiphe sp.* (on Chrysanthemum), showing the haustoria. h., d., from above; b., in section (× 400).
+
+137
+
+172
+BOTANY
+
+cells of the perithium there are developed curious appendages,
+upon the form of which the genera are largely based (Fig. 137, A).
+Of the higher Pyrenomycetes, those are peculiar to the pho-
+phytes, namely, those on dead wood, such as Xylaria, Cony-
+ceps, Pleospora, Sordaria, are among the common genera. The large
+black masses of Xylaria are sometimes very conspicuous upon dead
+wood. Certain species of a plant genus, such as *C. militaris* and
+*C. purpurea*, attack insects, especially caterpillars, which are killed
+by them. *Claviceps purpurea* causes the disease known as "Ergot"
+upon Rye. In many of these the ascospores are multicellular.
+
+![]() A B C D E F
+
+Fig. 130. — Black-knot (*Pirianaphes mali*).
+
+A. Fungum attacked by Black-
+knot. (Natural size.) B. conidia. C. stylospores.
+D. ascus with paraphyses and paraphyses showing ascus and paraphyses. E. single ascus, with two paraphyses, more highly magnified. F. germinating ascospore. (A–F, after FARLOW.)
+
+As a type of the higher Pyrenomycetes, we may select a very striking form of the earlier group, *Chalarae* (Fig. 138), a fungus causing destructive
+disease of plums and cherries, known as "Black-knot." The mycelium grows
+within the tissues of the younger twigs, where it produces unusually rough swell-
+ings which are called "black-knot."
+
+In the spring the mycelium shows active growth, and breaks through the outer
+layers of the bark, upon which it produces dense masses of conidia, borne upon
+rather thick stalks (Fig. 139). These conidia are so numerous that they may be
+described as a distinct genus under the name of *Chalarae*.
+
+As the season advances, however, the mycelium becomes more compact and the outer part may be detected the young perithecia, which were present, however, earlier in the sea-
+son. These form little papillae with a pore at the apex opening into the cavity within.
+Each one contains two spores, but instead of paraphyses may be seen living the perithecia, but the ascus are not ripe until later on.
+
+![]() Illustration showing a black-knot fungus attacking a plum twig.
+
+THE FUNGI 173
+
+The ascospores escape early in the spring, and probably infect the tender shoots of the host as they emerge from the soil.
+
+Stylospora, in cavities, much like the perithecia, there are found in smaller numbers the stylospores, single spores, divided into four cells (C) and borne upon long stalks (D).
+
+Spermogonia. — Another form of reproductive bodies is the Spermogonia, or Pyrindia, small receptacles like the perithecia, but containing many extremely small bodies which are not seen in most examples by a simple magnification. It is possible that these may be male reproductive cells, but this is by no means certain.
+
+![]()
+A mature plant, with anthorhiza, 5, and carpoconium, car.
+B young peritheium, section; 1, sex.; C ripe sexus.
+D ascospore.
+E germinating ascospore. F Lathraeastrum empressum. (All after Thaxter.)
+
+
+Fig. 140. — A. Stylospora pyrindia. A mature plant, with anthorhiza, 5, and carpoconium, car. The trichogyne, t, has numerous spermatia attached to it.
+B. young peritheium, section; 1, sex.; C. ripe sexus.
+D. ascospore.
+E. germinating ascospore. F. Lathraeastrum empressum. (All after Thaxter.)
+
+Order VIII. Laboulbeniaceae (Thaxter, 21)
+
+Our knowledge of this remarkable order of Fungi is principally due to the important researches of Professor Thaxter. They are minute forms parasitic upon insects, especially beetles, the majority attacking such forms as are active during the day. Living on the surface of the insect they are produced as a result of fertilization of an organ which closely resembles the procarp of the higher Rhodophyceae, and fertilization is effected by means of aperitif which attach themselves to the trichogyne of the female gamete. The aperitif consists of a conical ciliary cell, and each ascus contains four or eight spores, which are generally two-celled. The germinating ascospore attaches themselves to the surface of the insect, and form a more or less developed haustorium which may penetrate into the host, but the host is not killed by the attack of these fungi, as is the case with most other entomogenous Fungi (Fig. 140).
+
+174
+BOTANY
+
+**Class II. Basidiomycetes**
+
+The second great division of the Eumycetes, the Basidiomycetes, comprises a large number of the most conspicuous and highly developed fungi, such as the mushrooms, toadstools, rusts, smuts, etc. They always possess a well-developed mycelium, which may be composed of quite distinct elements, or these may be closely compacted into rodlike masses, or leathery plates, which grow to great size. The latter type is found in some Fungi which grow upon decaying wood and form the tough leathery stratum between the woody layers.
+
+**Reproduction.**— Various forms of sexual reproduction but the characteristic type is basidiospore. The basidiospores are single conidia borne upon special structures, basidia, which are usually undivided club-shaped cells, upon whose head the spores are pro- duced, attached to delicate prominences, the stigmata (Fig. 147, F). The basidiospores are often surrounded by a wall formed by the stegera, which passes part of the protoplasm from the basidium. The spore usually develops a thickened wall, but in the lower forms like the Rusts and Smuts the wall of the basidiospore remains very delicate, and in some cases is wanting altogether (Fig. 148, A). In the lower types (Hemibasidi) the basidia are divided by septa, and are less constant in form than those of the higher types (Eubasidi), which are also in most instances arranged in a definite hymenium covering the stigmata (Fig. 148, B). This arrangement is not nearly so evident in the lower members of the class. The latter are largely parasitic upon flowering Plants, while the Eubasidii are for the most part saprophytes.
+
+The Basidiomycetes are divided into two series, the Hemibasi- didii, a small group of parasitic forms in which the basidia arise directly from certain resting-spores; and the Eubasidii, in which true basidia are found which do not, as a rule, arise directly from resting-spores. Of the Hemibasidii the greater part are the so- called Smuts (Ustilaginae), very destructive parasites upon many of the higher plants.
+
+**Subclass I. Hemibasidii**
+
+The Ustilaginae derive their popular name from the masses of sooty-black spores which they produce on their hosts. Similar to these are American smuts is the common Corn-smut (Cochliogonum maydis), which so commonly attacks the flowers and young ears of Indian-corn. The sprouting corn is infected soon after it appears above ground by a fungus which grows through its tissues and causes the White-rust within the tissues of its host. While the mycelium grows for the most part in the intercellular spaces, it sends suckers into the host-cells and the hyphae may themselves penetrate into the cells. The hyphae are septate, thick-walled, and irregular in outline.
+
+![]() A diagram showing various stages of fungal reproduction.
+
+THE FUNGI
+175
+
+Reproduction. — As a rule the formation of spores is confined to the flowers of the host, but almost any part of the plant may show the galls containing spores. In the Corn-antum (Fig. 141) the spores may be formed either in the male flowers or in the female flowers forming the younger ear. The infected tissue becomes dark brown and enlarged, so that a single kernel may become as large as a walnut. A section of such a gall shows a densely branched irregular mycelium of the Smut packed in the intercellular spaces between the cells of the kernels. At the ends of the short branches myriadas of small black spores are seen, which give rise to new galls. The mass of spores is surrounded by a thickening white tissue giving the peculiar light color to the hypertrophied kernels, which are finally consumed by the insect.
+
+The spores do not germinate at once, but remain until the next season, when they germinate by sending out a short, thick hypha which grows into a spherical cell, each giving rise to a single conidium. The conidia may multiply by budding, very much like the Yeast-fungus, if grown in a fluid medium. Ordinarily the conidium grows by sending out a germ-tube which penetrates the delicate tissues of the host as it appears above ground, and leaves its affection by the parasitism.
+
+Tilletiaceae. — A second order of Smuts, the Tilletiaceae, contains also a number of destructive parasites. *Tilletia triticis* causes a serious disease of wheat, and *Urocystis oryzae* is very destructive to Strawberries.
+
+The genera *Gymnosporangium*, *Ustilago*, and *Marasmius*, especially species of Arrow-head (Sagittaria).
+
+SUBCLASS II. PROTOBRASIDIOMYCETES
+
+These resemble in some respects the Hemibasidiomycetes, and differ from the Autobasidiomycetes, or higher forms, in having the basidia divided. There are two orders, Auriculariaceae and Tremellaceae. The most important members of the first order are Stain (Utriculinae), *Auricularia* resupinate, whose name resents to *Utricula* gines, and like them among the most destructive of plant-parasites.
+
+![]() A B C D
+Fig. 141.—Gallina megalopis. A, staminate flower of Indian-corn, attacked by Smuts; B, mycetium, showing the branching mycelium; C, ripe spores (> 600). D, germinating spore with germ-tube emerging from it; E, mycelium, with sporidia, sp. (*D*, after Barraclough).
+
+176
+BOTANY
+
+They are endoparasites; the mycelium, which is often colored orange by the presence of an oily pigment, grows vigorously within the host, upon which sometimes there are produced distorted growths or galls.
+
+While the Smuta produce but one type of spores, many of the Rusts are characterized by the production of several quite different forms. This is especially true of the genus *Uredinum* (Ure- dium); i.e. the different stages may be borne upon entirely different hosts, often quite unrelated. This has resulted in much confusion in naming the Rusts, as different stages of the same plant have been named under the impression that they belonged to quite unrelated Fungi.
+
+Five forms of spores are known, the *Ecidiospores*, *Uredospores*, *Telosporia*, *Sporidia*, and *Spermatoria*. The last named are very minute oval or spherical bodies, usually contained in a cup-shaped receptacle (Pycnidia, Spermogonia), which usually accompany the *Ecidia*. It has been supposed that the spermatia may be male reproductive cells, but there is no direct evid- ence as to their real nature, no organon being cor- responding struc- ture having been demonstrated in any of them.
+
+The duration of the mycelium in the Rusts is vari- ous; some attach the host as an annual, the life of the parasite may be limited to a few weeks, but where the host is peren- nial, the mycelium may persist from year to year, grow- ing with the de- veloping tissues of the host-plant, upon which produces new crops of spores.
+
+The number of Rusts is very large, probably not far from two thousand species, which may be arranged in two categories, the
+
+![]() A diagram showing a section of a leaf of *Artemisia* repens, with pycnidia (x 300). B, section of spermogonium. C, section of ripe ascidium (x about 40); p., peridium.
+
+Fig. 14. — *Uredinae culatae.* A, section of the leaf of *Artemisia* repens, with pycnidia (x 300). B, section of spermogonium. C, section of ripe ascidium (x about 40); p., peridium.
+
+THE FUNGI 177
+
+Autecious forms, in which the different kinds of spores are produced upon the same plant, and the Heterocious forms, in which the sexi-
+dors are produced upon another host, as in the Wheat-rusts and the Cedar-rust.
+
+Of the former type a common species in the Eastern United States is *Puccinia* **caulis** (Fig. 142), which often appears in great numbers upon the leaves and sometimes upon the stems of the Tobacco-plant, *Nicotiana tabacum*, and also upon the Tobacco-bush, *Solanum lycopersicum*. The diseased leaves have the leaves much reduced in size, and thickly covered with the small yellowish pusules caused by the caulis, or first form of spore, and with the larger blackish pusules caused by the telosporic spores. The surface of the infected leaves will also show minute blackish specks, the spermonia. A section of the leaf shows the crowded mycelial threads occupying the inter-
+cellular spaces between the epidermis and mesophyll. The young sporangia are to form. The young ascidium is a globular mass of hyphae, from whose ends chains of basidiospores are cut off. These have colorless walls and orange-red, oily contents, and under pressure appear polygonal in shape. In some cases, when the basidia develop similar chains of cells, which become thick-
+walled and dark-colored so that they form a distinct receptacle which encloses the mature spores. This recepta-
+ture constitutes the *Acidium*, or ascidium fruit. This breaks through the epidermis of the leaf, and the ascidium opens, so that its contents are exposed to air, and as the pressure on the spores is relieved, they become rounded and fall off as spores.
+
+*Telosporia* --- If two or more plants are examined a few days apart, one will be found similar pusules, which appear black, and on examination will be found composed of single, thick-walled spherical spores. These are the *Telosporia*, and in this species perithecium only occurs once a year (probably not until the next spring).
+
+In California an extremely common Rust is *Puccinia malucocerum* (Fig. 143), which is especially abundant upon *Malva horealis*, but also causes much damage to the Hollyhock in gardens. Teloto-
+
+![]() A: A section of a leaf showing mycelial threads between epidermis and mesophyll.
+![]() B: A section of a leaf showing chains of basidiospores cut off from basidia.
+![]() C: A section of a leaf showing a globular mass of hyphae from whose ends chains of basidiospores are cut off.
+![]() D: A globular mass of hyphae from whose ends chains of basidiospores are cut off.
+
+Fig. 143. --- *A.* *Puccinia malucocerum*, upon Malva horealis. --- *B.* *Puccinia phyllicum*, upon Phlomis phyllicum, with some of teleutosporae (*x about 500*). --- *C.* *Puccinia phyllicum*, Buredo-
+spores of *P. prominens*. (After Sacchi.)
+
+178
+
+178
+BOTANY
+
+spores only are developed, and those germinate as soon as they are ripe. From each of the two cells, a short tube (Basidium, Fru-om- cium) is sent out, into which pass all the spore-contents. The basidium divides usually into four cells. Each of these develops a single sterigma, which swells at the end, and forms the single spo- ridium into which all of the contents of the basidium are poured. The sporidium germinates at once, sending out a short tube which, ably, as in other cases observed, enters the host-throat or stomata.
+
+Gymnosporangium.
+Of the heterocious Rusts, one of the most striking is Gymno-sporangium,
+in which there are several species causing
+the "Cedar-apple," gall-like excrescences
+(Fig. 144), upon the twigs of the Juniper
+and Red-cedar. If these galls are found in the early spring, the sur-
+face shows slight eleva-
+tions, beneath which masses of white delto-
+spores may be found.
+
+Fig. 144.--Gymnosporangium macrosporum. A, "Cedar-
+apple" gall; B, young sporangia; C, mature sporangia, ap.
+masses of teleutospores, ap. (Natural size); D, young
+two-intestinum, in one of the promyces; pr., has
+moss on it; E, young sporangia; F, mature sporangia,
+D, leaf of Cortusa vulgaris, with the seidum
+(Bassett's) on it.
+
+As these mature, they
+burst through the epi-
+dermis and appear as
+little orange-colored spikes (Fig. 144, A). These consist of masses
+of spores which are of globoidenous
+consistence, and swell up into large masses of yellowish jelly, when they are wet. Spores taken from such a mass may be found germinating, much as those described for the Mallow-rust.
+Sometimes instead of one or two spores, the promyces divide
+into joints which separate as single spores.
+
+The sporiae germinate promptly, but will not infect the Cedar.
+If placed upon the young leaves of Apple or Hawthorn, however,
+the germination is permanent. In a few days after this period weeks
+there will be produced orange-colored, somewhat thickened spots,
+upon whose upper surface the black spermonia are borne; upon
+the lower side, the acidia appear, which were first described under
+
+![]() A small illustration showing a microscopic view of a plant structure.
+
+Pr
+
+THE FUNGI 170
+
+the generic name, Rostelia. The wall of the ascidium is very much developed, and finally protrudes as a long tube (Fig. 144, D). The aecidiospores are produced upon the leaves of the infected Wheat. Heterocerus was first observed on one of the Wheat-rusts (Puccinia graminis) whose ascidia are produced upon species of Berberis. Upon the Wheat two sorts of spores are borne, the red-rust, or ureospores, long-cylindrical unicellular spores (145, D), and the black-rust, or teleosporae, which are small and mature late in the season, entering the young leaves through the epidermal cells, and rapidly spreading the rust. The teleosporae appear later, generally upon the same leaf, and remain dormant during the winter in the black-rust, but in the stubble, forming the spore-bodies of the sporidia, which in the spring infect the young Barberry leaves.
+
+The commonest species of Wheat-rust in the United States is *Puccinia rudis*—a plant which is universally diseased. This species forms its spores upon various plants, including the Borago officinalis, or Hound's-tongue (Cynoglossum), but the infection of the wheat is mainly due to the ureospores developed from the mycelium which has passed the winter within the wheat-plant—often the "volunteer wheat"—or possibly other Grasses.
+
+![]() A small illustration showing a magnified view of a plant structure with a focus on a specific part.
+A
+
+The Auriculariaeae
+This is a small family of which the best known is the genus *Auricularia*, a delicate, unspicuous, ear-shaped fruit-bodies upon rotten wood. The spores in these forms are borne upon jointed basidia, much like those of the Rusts.
+
+Order II. Tremellineae
+The Tremellineae resemble the Auriculariae in having the basi-
+dia divided, but in these the divi-
+sion is longitudinal, the spores
+being formed into short, long
+sterigmata, which are in two or
+four, resulting from the split-
+ting of the primary basidium
+(Fig. 143). Various species of
+Tremella are common upon dead
+Figs. 146.—d., Tremella sp., gelatinous
+mushroom-like fruit-body; e., *T. lutea*
+(Natural size); e., *R. conidia*, coni,
+and basidiospores; e., *T. lutea* (× 800).
+([after Bresadola])
+
+190
+BOTANY
+
+twigs, etc., where their bright orange-yellow or amber-colored gela-
+tinous fruit-bodies are conspicuous.
+
+SUBCLASS III. AUTORASIDIOMYCETES
+
+The greater number of the more familiar larger Fungi belong to the
+Autorasidiomycetes, of which the Tootsolds and Puffballs are the types. The lowest members of the group do not form a definite
+fruiting-body, but in most of them this is large and of very charac-
+teristic form.
+
+Order I. Exobasidium
+
+Among the simplest members of the
+Autorasidiomycetes, are the Exobasi-
+diums, represented by the genus Exo-
+basidium, which is widely distributed.
+It is widespread throughout northern re-
+gions, where it attacks Cranberry,
+(Phylica), and other plants. The
+plant is strictly parasitic, growing
+within the intercellular spaces of the
+host, and producing on its exter-
+nary gall-like deformations of the
+host. The outermost parts of the infected
+parts are sometimes entirely destitute
+of chlorophyll and present a pink or
+white appearance.
+
+Fig. 136.—Exobasidium Fastidif. A,
+flower of Menisella, hypertrophied by Exobasidium. (Natural size.) B,
+spores upon a flower (× 250). (After
+WORMSD.)
+
+The spores are borne upon basidia of
+typical form, which are developed from
+the hyphae of the host, and which break through the epidermis of the host.
+
+Order II. Hymenomycetites
+
+The Hymenomycetites comprise more than ten thousand species,
+—the largest number of the Fungi,—and exhibit great variety in the
+character of both the mycelium and the fruiting parts.
+
+Mycelium. The mycelium always consists of septate hyphae,
+which may be loose and delicate in texture, but more commonly
+are compacted into rodlike straights, or sometimes hard masses or
+sclerotia. In some species, such as those of wood, the mycelium
+grows between the layers of wood, and develops continuous leathery
+or papery layers of great extent. In such forms as the common
+Mushroom, the mycelium spreads widely through the substratum,
+which it binds together, so that large masses can be taken out,
+which consist in part of living mycelium. This constitutes the
+"spawn" of the Mushroom which is used for propagation.
+
+![]() A diagram showing three different stages of a fungus's growth.
+
+THE FUNGI
+181
+
+**Biology.** — Most of the Hymenomycetinæe are saprophytes upon dead vegetable matter, but a few are parasites, like certain species of *Fusarium* (Fig. 140, A), which grow on the roots of plants, and upon the trunks of trees, into whose living tissues the Fungus penetrates through wounds in the bark.
+
+**Reproduction.** — No form of sexual organ has yet been certainly demonstrated in any of these Hymenomycetinæe, and the large fruit-bodies arise as vegetative growths from the mycelium. In most of them basidiopores only are known, but conidia borne upon branching hyphae have been found in some species, e.g. Coprinus (Fig. 140, B). The spores are usually small and minute, or very minute, which may cover the whole surface of the fruiting-body, but is more commonly restricted to certain definite regions, such as the "gills" of the Mushroom.
+
+The fruit-bodies are made up of more or less closely compacted hyphae, which may be grown together, or so as to resemble a true parenchyma. In the persistent fruits, such as that of Polyporus, the walls of the cells are hard and woody in texture, but they are more commonly delinquent in the deciduous fruits, which contain numerous containing pigments, and extensive milk-tubes, occur in some species.
+
+The mycelium, in the larger forms, lives for many years, growing constantly and producing successive crops of fruits, or occasionally the fruits being destroyed by decay.
+
+**Classification.** — The classification of the Hymenomycetinæe is based upon the form of the fruiting-body and the arrangement of the hymenium. In the simpler forms like Clavaria (Fig. 140, A), the hymenium is a thin layer upon the upper surface of a flat fruiting-body. In Hydnum (Fig. 140, B) the form of the fruit varies, but the hymenium is confined to the pointed spikes which grow from certain portions of its surface.
+
+The better-known members of this order belong to the families Polyporaceæ and Agaricaceæ. The former include many conspicu-ous forms, of which the genus Polyporus is the type. To these belong the large, massive shelf-shaped Fungi, which grow upon the trunks of trees. The fruiting-body is a cup-like structure called *Pleurotus*, which has an umbrella-shaped fruit, like a Mushroom, from which it differs, however, in the arrangement of the hymenium. This in all the Polyporaceæ lines the walls of tubular, or more open cavities, which appear as small pores upon the under surface of the fruit (Fig. 140, C).
+
+**Agaricaceæ**
+
+The Agaricaceæ comprise all the common Fungi known popularly as Mushrooms and Toadstools, and are characterised by the well-known umbrella-shaped fruiting-body, bearing upon the lower face of the cap the dependent lamellæ or gills, upon whose surface the hymenium is borne.
+
+182
+BOTANY
+
+Most of the Agaricaeae are saprophytes, growing most commonly upon soil rich in humus or decaying vegetable matter, but many of them grow upon animal excrement, like the common genus Coprinus (Fig. 147). The fruit-body of this genus appears spontaneously upon horse-masure which is kept for a week or two under a bell-jar. The common field Mushroom (Fig. 148), also, grows especially well in pastures which have been enriched by the drop-
+pings of animals.
+
+![]() A mushroom with a long stem and a cap that is slightly expanded.
+![]() B A-H, development of the fruit-body in *Coprinus* sp. A-C, slightly enlarged, the others more highly magnified. D, section of young lamella. E, hymenium of young lamella. F, young basidiospores. G, H, young fruit-bodies. I, conidia of *C. inopinus*. (J. after BURKELL.)
+
+The mycelium in these forms spreads extensively through the substratum, and the Mushroom must have a long period of growth before its fruit-body begins to develop. Occasionally, in *C. inopu-
+pus*, branching filaments may arise from the mycelium, upon which conidia are borne; but usually the only type of spore developed is the basidiospore.
+
+The formation of the fruiting-body begins in a small, compact mass of hypha (Fig. 147, G), which are at first entirely similar. In most
+
+![]() I A young plant with a slender stem and leaves.
+![]() II A young plant with a slender stem and leaves.
+![]() III A young plant with a slender stem and leaves.
+![]() IV A young plant with a slender stem and leaves.
+![]() V A young plant with a slender stem and leaves.
+![]() VI A young plant with a slender stem and leaves.
+![]() VII A young plant with a slender stem and leaves.
+![]() VIII A young plant with a slender stem and leaves.
+![]() XII A young plant with a slender stem and leaves.
+![]() XIII A young plant with a slender stem and leaves.
+![]() XIV A young plant with a slender stem and leaves.
+![]() XV A young plant with a slender stem and leaves.
+![]() XVI A young plant with a slender stem and leaves.
+![]() XVII A young plant with a slender stem and leaves.
+![]() XVIII A young plant with a slender stem and leaves.
+![]() XIX A young plant with a slender stem and leaves.
+![]() XX A young plant with a slender stem and leaves.
+![]() XXI A young plant with a slender stem and leaves.
+![]() XXII A young plant with a slender stem and leaves.
+![]() XXIII A young plant with a slender stem and leaves.
+![]() XXIV A young plant with a slender stem and leaves.
+![]() XXV A young plant with a slender stem and leaves.
+![]() XXVI A young plant with a slender stem and leaves.
+![]() XXVII A young plant with a slender stem and leaves.
+![]() XXVIII A young plant with a slender stem and leaves.
+![]() XXIX A young plant with a slender stem and leaves.
+![]() XXX A young plant with a slender stem and leaves.
+![]() XXXI A young plant with a slender stem and leaves.
+![]() XXXII A young plant with a slender stem and leaves.
+![]() XXXIII A young plant with a slender stem and leaves.
+![]() XXXIV A young plant with a slender stem and leaves.
+![]() XXXV A young plant with a slender stem and leaves.
+![]() XXXVI A young plant with a slender stem and leaves.
+![]() XXXVII A young plant with a slender stem and leaves.
+![]() XXXVIII A young plant with a slender stem and leaves.
+![]() XXXIX A young plant with a slender stem and leaves.
+![]() LXII A young plant with a slender stem and leaves.
+![]() LXIII A young plant with a slender stem and leaves.
+![]() LXIV A young plant with a slender stem and leaves.
+![]() LXV A young plant with a slender stem and leaves.
+![]() LXVI A young plant with a slender stem and leaves.
+![]() LXVII A young plant with a slender stem and leaves.
+![]() LXVIII A young plant with a slender stem and leaves.
+![]() LXIX A young plant with a slender stem and leaves.
+![]() LX XIX A young plant with a slender stem and leaves.
+![]() LX XII A young plant with a slender stem and leaves.
+![]() LX XIII A young plant with a slender stem and leaves.
+![]() LX XIV A young plant with a slender stem and leaves.
+![]() LX V I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+i
+
+THE FUNGI
+183
+
+forms thin shows a central more compact body surrounded by a weft of loose filaments, which completely invests the young fruit-body. In *Coprinus* the cap is formed by a cap-like structure (Pileus) at the top of the short, thick stalk. The cap, which is flat at first, grows downward over the stalk, which it completely covers. As the cap develops, there are formed upon its inner surface the radiating lamellae (Gills), which are composed of numerous gills. A section of the gill shows that the inner tissue (Trama) is composed of large, rather loose hyphae, much like those forming the body of the fruit. The ends of these hyphae are turned outward and form a layer of spore-producing cells (Basidiospores). The outermost gill. This superficial layer is the hymenium, and some of its cells become later transformed into the basidiospores, while others remain sterile. Some of these sterile cells may become very much enlarged and form the "Cystidia."
+
+![]() A mushroom (Psalliota compta) with fruit-bodies in various stages of development. B-D, sections of young fruit-bodies, showing the development of this fruit. (All after ARTHUR.)
+Fig. 148.—Mushroom (*Psalliota compta*). A, mycelium with fruit-bodies in various stages of development. B-D, sections of young fruit-bodies, showing the development of this fruit. (All after ARTHUR.)
+
+The basidiospores are club-shaped bodies tapering below and somewhat flattened at the top, from which grow the sterigmata, which are usually four in number, but may be reduced to two or three (Fig. 147, E, F).
+
+Development of Spores.--The development of the basidiospores has been specially studied by ARTHUR (1871). In the young basidiospores there are two or more nuclei. These fuse into a single one, which later divides into four, corresponding to the four spores. The sterigmata begin to form after this division is complete, and each nucleus passes through a stage in which it becomes elongated and then reaches their full size, and sometimes develop the brown walls, before the nuclei pass over from the basidiospores. The way in which the nuclei pass through the walls is shown on the next page, which was clearly demonstrated. After entering the spore, the nuclei divide into two.
+
+![]() A mushroom (Psalliota compta) with fruit-bodies in various stages of development. B-D, sections of young fruit-bodies, showing the development of this fruit. (All after ARTHUR.)
+A B C D
+
+184
+BOTANY
+
+When the fruit is complete, there is, in Coprinus, a very rapid elongation of the stalk, due to absorption of water and great stretching of the cap.
+
+A
+![]() A mushroom with a long, thin stalk and a large, round cap.
+
+B
+![]() B shows a mushroom with a short, thick stalk and a small, round cap.
+
+C
+![]() C depicts a mushroom with a long, thin stalk and a large, round cap.
+
+D
+![]() D shows a mushroom with a short, thick stalk and a small, round cap.
+
+E
+![]() E illustrates a mushroom with a long, thin stalk and a large, round cap.
+
+F
+![]() F depicts a mushroom with a short, thick stalk and a small, round cap.
+
+Fig. 149. — A. *Clitocybe* orestis. (Natural size.) B. *Agaricus* rumensum. C. *Polyporus* sp. D. *Auriscalpium* sp. E. *Coprinus* sp. F. *Hymenomycetes*, with basidia. (B, after Sprengel.)
+
+The cap takes place somewhat laterally. The gills are developed which is only exposed when the spores are ripe. The longitudinal section through the young Mushroom shows two small cavities, which are connected by a circular canal, which separates the cap from the stalk. Almost completely filling this canal are the basidia. The upper face of the cap. At first the cap is no broader than the stalk. The hymenium is connected by a continuous layer of tissue—the Volum. As the lateral growth of the cap proceeds, the hymenium torn away and the gills are exposed. The remains of the hymenium surround the upper part of the stalk. The lower parts of the elements of the volum may often be seen bringing the margin of the cap.
+
+The Agaricaceae are the largest family of Fungi, including nearly two thousand species. Many of them are among the most valuable of edible Fungi, such as the true Mushroom (*Agaricus* *pallidus* *comptus*), the Chanterelle (*Cantharellus cibarius*), and many others. On the other side (Fig. 150) — Lepiota nucansn.
+
+(After Arnaud.)
+
+THE FUNGI
+185
+
+hand, some of them are extremely poisonous. Of the latter, the deadly Agaric (Amanita phalloides) is sometimes mistaken for the true Mushroom, from which, however, it differs very much. It has white gills and the cap, when wet, is slimy. Moreover, it grows from a sort of cup or volva, which is quite absent from the edible Mushroom. The most poisonous species is the Fly-agaric (Ama-
+nita muscaria). It may be recognized by the bright yellow or red pileus covered with warty scales.
+
+**Gasteromycetes**
+
+The highest orders of the Basidiomycetes are often grouped together under the name Gasteromycetes, which are distinguished from the Hymenomycetese by having the spores borne within closed chambers, so that the interior of the fruit often shows a honey-combed structure. A fruiting-body may reach a very large size, as in the Giant Puffball (Puffball), where it may be thirty to forty centimeters in diameter. Most of the so-called hemi-an-
+giocarpous Hyme-
+nonycoetes are to some extent inter-
+mediate in charac-
+ter between the
+lower ones and
+the more special-
+ized Gasteromyce.
+One very remarkable order,
+the Pucciniaceae,
+which is often in-
+cluded with the Gasteromycetes, is also somewhat intermediate in character between them and the Hymenomycetese. In the Phal-
+luses these spores are enclosed within thin wall cham-
+bers, but when the spores are ripe, the tissue to which they are attached breaks through the outer covering of the fruit, and the spores are thus exposed.
+
+![]()
+A. C. Hypholoma capense. A. ripe fruit-body (< 1); u, volva; pd, gleba. B. mycelium with young fruit-body, slightly reduced. C, section of nearly mature fruit-body. D, spores of Aspergillus herbarius. (D after Scow.)
+
+
+Figs. 131—134.
+
+106
+BOTANY
+
+Order III. Phallinum
+
+The development of the fruit has been carefully studied in several forms, among them the ubiquitous Phallus impudicus, or "Stink-horn," so called on account of its disgusting odor (Fig. 151).
+
+Upon the subterranean mycelium the fruit-bodies are borne much as in the Mediterranean species, but they are much smaller and more delicate in color. These enlarge until they are nearly as large as a hen's egg, and on sectioning such a young fruit it is found to consist of an outer white shell, the Peridium, and a central-body of very complicated structure (Fig. 151, C). The latter consists of a central elongated hollow core, which extends the whole length of the central body, and is surrounded by a series of thin-walled sac-like struc-
+ture, whose interior is divided into chambers lined with the hymenium. This spore-bearing structure is the "Gloea." At maturity the cylindrical core elongates very rapidly, and becomes covered with a series of short, thick-walled, egg-shaped globs upon a stout hollow stalk. The tissues of the fruiting-parts are very mucilaginous, and the spores are surrounded by a slimy fluid, which gives off a most disagreeable odor.
+
+In the curious genus Clathrus the complete central-body has the form of a hollow lattice-work, which is bright red in color.
+
+![]() A B C D E F
+
+FIG. 152. --A, Lyngberus calcaratus (x 3); B, Greater sp. (x 1); C, basidia of G. regeneris; D-F, Cyatium striatum (x 2). (C, after TULANZ.)
+
+THE FUNGI
+187
+
+Order IV. *Lycoperdineae*
+
+The best known of the Gasteromycetes are the Puffballs, of the genus *Lycoperdon* (Fig. 152, A). The large fruits are globular, oval, or pear-shaped solid bodies, often of large size. A section through the young fruit shows a dense white or apparently homogenous mass of spores, composed mainly of membrane lined with the hymenium. As the fruit develops, the wall becomes differentiated into a firm, somewhat leather peridium, which in the genus *Geaster* (Earth-bear) is double, with a stem-like tissue between, and in some species is composed of delicate threads (Capillitium), which finally become completely disintegrated, and others whose walls become hard and persistent, and form much-branched threads (Capillitium) which remain attached to the fruit throughout its life with the ripe spores. At maturity, the peridium breaks, and the powdery mass of spore is discharged. In *Geaster* (Fig. 152, B), the outer peridium splits into strips, which bend back, exposing the inner peridium, within which are contained the spores. The outer peridium is strongly hygroscopic.
+
+Order V. *Nidulariae*
+
+The curious little Fungi of the genera *Nidularia* and *Cyathus* (Fig. 152, D-F) differ from the Puffballs in having the spore-chambers surrounded by a separate peridium, so that they form little bodies, $sp$, lying within the open outer peridium, like eggs in a nest, hence the popular name of bird's-nest Fungi for these little plants.
+
+LICHENS
+
+The remarkable group of Fungi known as Lichens do not constitute a natural morphological group, as its members belong to several well-marked classes among the Basidiomycetes; the greater part belonging to the former class. These Fungi are intimately associated with certain low Algae or Chlorophyseae, upon which they are parasitic to a greater or less degree. The Algae are usually green in colour, but may be brown or grey by the mycelium of the Fungus, or in some of the gelatinous Lichens, like Collema, the form of the Lichen is determined by the gelatinous Nostoc-colony, which is the host of the Fungus.
+
+The Lichens are not included in this class coordinate with the Algae and Fungi, it being supposed that the green cells, or "genidia," were outgrowths of the fungal hyphae. The researches of De Bary and Schwendener first showed that the green cells were
+
+188
+BOTANY
+
+really independent organisms, and these researches were followed by many others which soon placed the dual nature of the Lichen-thallus beyond any question. It has been conclusively shown that the Algae can live quite well or, better, when removed from their association with the Fungus, which, on its side, dies, if deprived of its algal associates, will not long survive without artificial nutritive food constituents. Careful experiment has also demonstrated the possibility of producing a Lichen-thallus by associating the germi-
+nating spores of the Lichen with Algae which were growing free,
+and Molton has succeeded in producing a Lichen-thallus by utiliz-
+ized glass plates, by supplying them with artificial nutrient, but eliminating the Algae from which the food ordinarily is derived.
+
+Germination.—Under normal conditions, the Lichen-spores, on germinating, produce a mycelium which grows outwards and com-
+ing in contact with the proper algal cells (Fig. 154. A) attaches itself to them and ultimately produces the complete Lichen.
+In case the green cells are not available, the mycelium dies as soon as it has reached the surface of the glass plate.
+
+The Algae which occur within the body of various Lichens are identical with species which also live quite independently. They represent most of the families of the Schizophyceae and several of the lower orders of the Chlorophyceae. The genus Pro-
+toococcaceae, although a few Conferances have also been found as the gonidia of Lichens. These Algae, when associated with the Lichen, multiply only by fission; but in some cases, at least, when removed from their host they may reproduce by budding.
+
+Parasitism and Symbiosis.—The amount of injury caused by the Fungus to the algal cells varies in different cases. Sometimes haustoria are sent into the cells, which are finally killed. Sometimes the haustoria remain in the cells and do not injure the protoplast. In still other instances, there is no penetra-
+tion of the algal cells, and the substances taken from them must diffuse through their walls. It is clear, however, that the association of the two organisms is beneficial to both parties. This is symbi-
+lism. It is true that the Algae may derive certain advantages in being protected by the enveloping Fungus filaments, which also retain water somewhat tenaciously, thus enabling the Algae to grow where water would otherwise be scarce. This form of association has been termed Symbiosis. A further remarkable phenomenon is the occasional parasitism of one complete Lichen upon another.
+
+Semi-Lichens.—A number of Ascomycetes have been de-
+scribed whose life history is similar during those stages, but later become associated with Algae, which as a rule are injured by the attacks of the Fungus. *Spheria lamanee* and *Thermia* *vulutina* are examples of the Half-lichens.
+
+THE FUNGI 180
+
+Distribution. — The number of Lichens is very large, and they are of almost universal distribution, their peculiar structure enabling them to live where scarcely any other vegetation is possible, this being especially the case on exposed rocks, where Lichens are among the first organisms to appear. They play a very important role in the decomposition of rocks, being by this means able to develop of special solvent substances, to disintegrate even such hard rocks as granite and gneiss.
+
+The hyphae of *Ver. rucaris marmorea* have been found to penetrate to a depth of nearly two centimetres into limestone upon which it was growing. Where the Lichen grows closely attached to the smooth bark of trees, as in the so-called crustaceous forms, it is often to a greater or less extent parasitic, penetrating into the tissues of the bark. Such forms are often deficient in the green algal cells.
+
+The Lichens show several well-marked types in the form of the thallus. This may be closely adherent to the substratum (Crustaceous); flat or leaflike (Foliaceous); gelatinous, or bushy (Fruticose); or a combination of these.
+
+Gelatinous Lichens. — The simplest type is shown in the gelatinous Lichens, where the independence of the two constituents of the thallus is evident. In these forms the Alga is usually a species of *Botryococcus* (Fig. 135, B), while the Fungus is a normal Nostoc-columella. The gelatinous mass is penetrated by the loose filaments of the Fungi, which finally produce the characteristic fruiting-bodies.
+
+In the more typical Lichens the hyphae are densely interwoven and form a tough, often leathery thallus, within which the algal
+
+![]() A sp
+![]() B
+![]() C a
+
+Fig. 135.—A, *Streptophorus*, a foliose Lichen (natural size). op., apothecia; b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z, showing the algal cells; a and the rhizoids; r (× 40), *Nostoc* filaments; *Streptophorus* surrounded by the fungal filaments (× 450).
+
+181
+
+100
+BOTANY
+
+cells are distributed, either without any definite order (Homoerous) or in definite layers (Heteromorous). In most of the prostrate forms the latter arrangement is the rule. A section of one of these forms shows the densely interwoven and often coherent hyphae forming a dense inner ring, beneath which is a somewhat looser stratum, in which the green cells form a continuous layer. The inner portion of the thallus may rise up loosely on short hyphae forming a sort of pith. The lower part of the thallus is usually quite destitute of green cells and often develops roothlike outgrowths, which fasten it to the substratum.
+
+The fruticose Lichens, such as the common Lichen of California, are attached by a small point in the latter sometimes only being held by small twigs upon which a fragment has fallen. In these forms it is evident that the point serves simply as a point of attachment.
+
+Where the conidia of the Lichen follow very closely the form of the Alga, which is only slightly different with the hyphae.
+
+Chemical Properties of Lichens. The young hyphae usually show the reaction of pure cellulose, but later the cell-walls become modified, forming either Fungus-cellulose or a change into a gelatinous substance, such as isoleucine, the latter substance turning blue on the application of iodine. The remainder, like that of a weak variety of peculiar products, such as special organic acids, pigments, and various excretory products, are also found in the Lichens.
+
+Reproduction
+
+The thallus of a Lichen may multiply by means of fragments torn off accidentally, or by the production of special bodies known as "Soredia." These consist of roundish bodies composed of a tangle of hyphae enclosing a number of the green cells. These soredia are sometimes formed in large numbers upon the surface or margins of the thallus, where they form a greenish gray powder. Conidia, or non-sexual spores like those of many ordinary Ascomycetes, occur in a
+
+![]() A diagram showing a cross-section of a lichen thallus.
+![]() B diagram showing a close-up view of a lichen thallus with green cells and hyphae.
+
+Fig. 153.—A, *Xanthoria parietina*, filaments and green cells; B, sporophore attaching itself to cells of *Fissarospora* (*x 900*). (After Du Hany.) A, filament sending a hair into contact with another cell (*x 900*). (After Du Hany.)
+
+154
+
+THE FUNGI 161
+
+very small number of Lichens, but are usually absent. Pycnidia, or sporegonia (Fig. 155, B), like those of the Rutsa, and many Ascomycetes, are of common occurrence. Minute conidia are pro-
+duced in these, and may germinate and produce a mycelium in many cases. The ascospores are sometimes made reproductive cells is still somewhat doubtful.
+
+With the exception of two genera of tropical Lichens (Cora and Corella), which produce basidiomycetes, the characteristic spores are ascomycetes, which are borne in fructifications very much like those of the typical Lichens. These spores are usually numerous, but their number, and may be either unicellular or multicellular (Fig. 155, C).
+
+![]() A small image showing a microscopic view of a fungal structure.
+Fig. 158. — A, Collemis microphylla, showing ascomogenous hyphae, with trichogyne, z. (After Suh.) B, sporegonium of Collemis sp. (× 45). C, Sticta palustris, and paraphyses of Aspergillus niger on ascomatous Lichen (Gymnos) growing on the bark of a Beech; ap., apothecia (× 3).
+
+The type of the fruit is either open (Apothecium), like that of the Cup-fungi, or closed (Peritheciurn), like that of the Pyrenomycetes.
+
+In the latter case, the ascus is developed within a sac-like formation of the apothecium is preceded by a specially modified,
+enlarged hypha, whose extremity forms a slender projecting struc-
+ture, which has been compared to the trichogyne of the Red Algae
+(Fig. 155 A). According to Suhal, this is utilized for the
+spermogonium from the male gametophyte. The question of actual
+fertilization has, however, been disputed. From this ascocarpium
+the apothecium, or at least the ascogenous portion is developed,
+much as in such a Cup-fungus as Pyronema. In most of the
+
+192
+BOTANY
+
+Lichens no trace of an ascogonium has been found, but the fruits arise in a strictly non-sexual manner.
+
+**Classification of Lichens**
+
+The Lichens may be divided into three orders, based upon their affinity with special groups of Fungi. These are: 1. Disulichenes; 2. Pyronichenes; 3. Basidiochenes. About two thousand species are known occurring in all regions. Some like the Reindeer-moss (Cetraria *Iridoides*), and the Lichen from which in immense quantities and are of value as food, especially to the Inuit, are large fruticose forms like *Usnea barbata*, *Ramalina fuciformis*, *Ramalina reticulata*, and the various *Evernia* *pyrolifera*, the apothecia horse upon cup-shaped branches or on the ground. The large fruticose forms like *Usnea barbata*, *Ramalina fuciformis*, *Ramalina reticulata*, and the various *Evernia* *pyrolifera*, the apothecia horse upon cup-shaped branches or on the ground. The large fruticose forms like *Usnea barbata*, *Ramalina fuciformis*, *Ramalina reticulata*, and the various *Evernia* *pyrolifera*, the apothecia horse upon cup-shaped branches or on the ground. The large fruticose forms like *Usnea barbata*, *Ramalina fuciformis*, *Ramalina reticulata*, and the various *Evernia* *pyrolifera*, the apothecia horse upon cup-shaped branches or on the ground. The large fruticose forms like *Usnea barbata*, *Ramalina fuciformis*, *Ramalina reticulata*, and the various *Evernia* *pyrolifera*, the apothecia horse upon cup-shaped branches or on the ground.
+
+Fig. 136. — A. *Ramalina reticulata*. (Natural size.)
+B. Ramalina reticulata, showing the very large terminal apothecia.
+C. Cladonia pyriformis.
+D. Cladonia pyriformis, showing the very large terminal apothecia.
+E. Cladonia pyriformis, showing the very large terminal apothecia.
+F. Cladonia pyriformis, showing the very large terminal apothecia.
+G. Cladonia pyriformis, showing the very large terminal apothecia.
+H. Cladonia pyriformis, showing the very large terminal apothecia.
+I. Cladonia pyriformis, showing the very large terminal apothecia.
+J. Cladonia pyriformis, showing the very large terminal apothecia.
+K. Cladonia pyriformis, showing the very large terminal apothecia.
+L. Cladonia pyriformis, showing the very large terminal apothecia.
+M. Cladonia pyriformis, showing the very large terminal apothecia.
+N. Cladonia pyriformis, showing the very large terminal apothecia.
+O. Cladonia pyriformis, showing the very large terminal apothecia.
+P. Cladonia pyriformis, showing the very large terminal apothecia.
+Q. Cladonia pyriformis, showing the very large terminal apothecia.
+R. Cladonia pyriformis, showing the very large terminal apothecia.
+S. Cladonia pyriformis, showing the very large terminal apothecia.
+T. Cladonia pyriformis, showing the very large terminal apothecia.
+U. Cladonia pyriformis, showing the very large terminal apothecia.
+V. Cladonia pyriformis, showing the very large terminal apothecia.
+W. Cladonia pyriformis, showing the very large terminal apothecia.
+X. Cladonia pyriformis, showing the very large terminal apothecia.
+Y. Cladonia pyriformis, showing the very large terminal apothecia.
+Z. Cladonia pyriformis, showing the very large terminal apothecia.
+
+BIBLIOGRAPHY
+
+91. 1. Atkinson, G. F., Mushrooms, Edible Poisonous etc., Ithaca, 1901.
+92. 2. De Bary, A., Fungi, Mycota, and Bacteria., Oxford, 1887.
+93. 3. Batsch, J., Die Pilze der deutschen Flora., Berlin, 1850-57.
+94. 4. Engler and Prantl., Naturliche Pflanzenfamilien., 1 Teilh., I Abt., 1862-97. (Bibliography of the special groups with each section.)
+95.-91. 5. Engler and Prantl., Die Pilze der deutschen Flora., 2nd ed., Berlin, 1898-1900.
+6. Engler and Prantl., Die Pilze der deutschen Flora., 3rd ed., Berlin, 1900-04.
+7. Engler and Prantl., Die Pilze der deutschen Flora., 4th ed., Berlin, 1904-07.
+8. Engler and Prantl., Die Pilze der deutschen Flora., 5th ed., Berlin, 1907-10.
+9. Engler and Prantl., Die Pilze der deutschen Flora., 6th ed., Berlin, 1910-12.
+10. Engler and Prantl., Die Pilze der deutschen Flora., 7th ed., Berlin, 1912-14.
+11. Engler and Prantl., Die Pilze der deutschen Flora., 8th ed., Berlin, 1914-16.
+12. Engler and Prantl., Die Pilze der deutschen Flora., 9th ed., Berlin, 1916-20.
+13. Engler and Prantl., Die Pilze der deutschen Flora., 10th ed., Berlin, 1920-24.
+14. Engler and Prantl., Die Pilze der deutschen Flora., 11th ed., Berlin, 1924-28.
+15. Engler and Prantl., Die Pilze der deutschen Flora., 12th ed., Berlin, 1928-32.
+16. Engler and Prantl., Die Pilze der deutschen Flora., 13th ed., Berlin, 1932-36.
+17. Engler and Prantl., Die Pilze der deutschen Flora., 14th ed., Berlin, 1936-40.
+18. Engler and Prantl., Die Pilze der deutschen Flora., 15th ed., Berlin, 1940-44.
+19. Engler and Prantl., Die Pilze der deutschen Flora., 16th ed., Berlin, 1944-48.
+20. Engler and Prantl., Die Pilze der deutschen Flora., 17th ed., Berlin, 1948-52.
+21. Engler and Prantl., Die Pilze der deutschen Flora., 18th ed., Berlin, 1952-56.
+22. Engler and Prantl., Die Pilze der deutschen Flora., 19th ed., Berlin, 1956-60.
+23. Engler and Prantl., Die Pilze der deutschen Flora., 20th ed., Berlin, 1960-64.
+
+Fungi issued by the Department of Agriculture.
+
+24. Frank, A.B.; Lehrbuch der Botanik; Leipzig; 1902.
+
+25.-30.. Halmann; Handbuch der Pflanzenlehre; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig; 3rd ed.; Leipzig;
+
+THE FUNGI
+193
+
+*79. 11. Laurenz, Chr. Handbuch der systematischen Botanik, Vol. I. Leipzig, 1879.
+*99. 12. Peirce, G. J. The Nature of the Association of Alga and Fungus in the Soil. Annals of Botany, Vol. 10, No. 56, pp. 385-390, 1866.
+*89-'92. 13. Saccardo, P. A. Syllage Fungorum, Vol. 1-14. Padua, 1882-92.
+*92. On the most important systematic work upon Fungi.
+*97. 14. Schleiden, M. W. Die Anatomie des Pflanzenreiches. Gottingen, N.Y., 1867.
+*98. 15. Guide to the Study of Lichens. Boston, 1868.
+*96. 16. Sowerby, F. T. The Compound Lobepes of Albany Blitl. Bot. Gaz. XXVII, p. 150.
+*17. Strasburger, E. T. On the Carpoyle Structure and Development of the Coleiaceae and Allied Groups. Proc. American Acad., Vol. XXXV.
+*90. 18. Sturzgk, W. C. On the Entomophthoraceae of the United States.
+*90. 19. Thaxter, Roland. The Entomophthoraceae of the United States.
+*96. 21. ———— On the Entomophthoraceae of the United States. Mem. American Acad., XII, No. II., 1866.
+*22. ———— Papers in the Botanical Gazette and elsewhere dealing principally with aquatic Fungi.
+*97. 23. Tubert, K. Diseases of Plants. Longmans, Green & Co., 1867.
+*96. 24. Underwood, E. M., Moulds, Milawa, and Mushrooms New York, 1866.
+*98. 25. Van Teghem, Ph., Traité de Botanique Paris, 1868.
+*96-97-98-99-100-101-102-103-104-105-106-107-108-109-110-111-112-113-114-115-116-117-118-119-120-121-122-123-124-125-126-127-128-129-130-131-132-133-134-135-136-137-138-139-140-141-142-143-144-145-XXXXX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+*98.-XXXIX
+o
+
+CHAPTER VII
+
+THE ARCHEGONIATE; MUSCINE.
+
+The Algae are typically aquatic plants, and even those forms which are adapted to life out of the water can vegetate only when an abundant water supply is present, and remain dormant when the supply is withdrawn. These plants reach their most perfect develop-ment in the sea, where the water supply is constant, and the highest expression of the algal type is seen in the large Red and Brown Algae.
+
+From the much simpler fresh-water Green Algae another group of plants has been derived which has far outstripped all other com-petitors, and has become the dominant form of vegetable structures. These are the terrestrial green plants which at present are the pre-vailing plant-types. The lowest of these terrestrial plants, the Archegoniate, show unmistakable evidences of their aquatic origin, and although they have no direct ancestors in the land-plants, so far as we know, as the direct ancestors of the land-plants, still there is strong evidence that the lower Archegoniates, the most primitive of the terrestrial plants, have arisen from forms allied to the existing Chlorophytes. On the whole, however, it would seem that the Chlorophytes are the Archegoniates, and of those the genus Coleochaete shows the nearest affinity, although the character of the reproductive organs in the Characeae also gives some suggestions of the archegoniate type. The Archegoniate type is thus a very ancient one.
+
+The substitution of an aerial for an aquatic environment was no doubt very gradual, and there are still some forms among the Green Algae and lower Archegoniates which show how this may have come about. The first step in this direction was probably a reduced water supply. Most fresh-water Algae are subjected to destruction by the drying up of the shallow ponds in which they grow, and their vegetative period may be very short. To provide against this danger they produce resting spores or cysts, which remain dormant until the supply of water is renewed. A few forms, like Botrytium and some species of Vaucheria, grow on the mud left by the receding water, but their growing period is entirely dependent upon a length of time during which the mud remains moist, and they also produce resting-spores at the end of their short vegetative existence.
+
+104
+
+THE ARCHEGONIATE.
+196
+
+In the lower Archegoniate, however, although they are more or less dependent upon an ample supply of moisture, the plant develops various devices for protecting it against the loss of water. Besides these, the plant has to protect itself against the drying up of its substratum and renew the supply lost by evaporation, which is, moreover, checked by the development of an imperious cuticle upon the cells exposed to the air. These devices, which are only imperfectly developed in the higher forms of land-plants, are characteristic in many of the higher types of land-plants. The conditions being so much more variable on land than in the water, the terrestrial plants show a correspondingly greater diversity of structure than is ever found in the aquatic forms.
+
+None of the Archegoniate possess motile cells corresponding to the non-sexual zoospores of the Algae, but all of them give rise to motile cells during their early stages of development. In this respect they differ from the archegonium which contains the egg; and this reversion to the aquatic condition as a preliminary to fertilization indicates the aquatic origin of all these forms.
+
+The formation of cysts or resting-spores occurs in all of the Archegoniate; but instead of resting-eggs developing at once into a resting-sporus, as it does in most Green Algae, the egg develops into a multicellular plant, the Sporophyte, which then gives rise, non-sexually, to a large number of resting-spores. One fertilization may therefore result in a large number of spores, whereas this is not the case among the Green Algae. The development of the carpospores of the Red Algae offers an analogy to this, although the method of spore-formation is totally different.
+
+In a few cases (e.g. Ricciocarpus, Fig. 183) the plant usually lives as an aquatic, but it may assume a terrestrial form by setting on the mud after the subsidence of the water, and there grow even more vigorously than it did when floating in fresh water. Sometimes the plant remains permanently in this position, and thus assumes the terrestrial form. The behavior of Ricciocarpus probably illus-
+trates the way in which the terrestrial Archegoniate first began to take possession of the land.
+
+With these plants the Archegoniate are sometimes put in a single great division, the Embryophyta, so called because the fertilized egg develops into a multicellular embryo before the spores are formed. All of the Archegoniate agree closely in the character of their sporophytes; and there is little question that the subkingdom is very natural one.
+
+Alternation of Generations.—All Archegoniate show two phases of development. The spore, on germination, produces a plant, the gametophyte, whose gametes are born to each sex reproductive organs,
+archegonia and antheridia. From the egg within the archegonium...
+
+106
+BOTANY
+
+after it is fertilized, is developed the embryo, which becomes a more or less highly organized plant, the sporophyte. The latter, sooner or later, gives rise to the spores, which are invariably produced in tetradic form from the sporophyte-fruit (Fig. 157). It has lately been suggested that the spore-fruit of the Red Algae may be considered as a sporophyte, but, aside from this, the nearest approach to the condition prevailing among the Archeogoniates is that found in the genus Coleochaete, where a rudimentary sporophyte is developed from the oospore.
+
+![]() A
+![]() B
+![]() C
+![]() D
+
+![]() E
+![]() F
+![]() G
+
+Fig. 157.--Medothea (Belliflorina) Bolanderi. Development of the archeogonium (× 300). C, cross-section of young archeogonium. G, cross-section of the neck of an older one. The oocytes are longitudinal sectors; b, ventral canaloid; o, egg.
+
+**Gametophyte.** --The gametophyte of the Archeogoniates may be a plant of large size, attaining a length of thirty forty centimeters or more; or it may be so minute as to be microscopic. Moreover, it may be reduced to a microscopically small body composed of a few cells, as in the male gametophyte of some Ferns. Whether large or small, the structure of the reproductive organs is remarkably uniform.
+
+**The Archeogonium.** --The archeogonium (Fig. 157) is usually a flask-shaped body composed of many cells, instead of being a single cell
+
+THE ARCHEGONIATE. 107
+
+like the oogonium of most Green Algae. The archegonium generally consists of a single superficial layer of cells, and an axial row of cells, of which the lowest one is the egg-cell. The upper part is the Neck, in which the neck-cells (or canal-cells) become disintegrated, and when water is applied, these swell up and burst open the apex of the neck, through which they are forced out, leaving a passage open to the venter, within which lies the egg, ready for fertilization.
+
+The archegonium of *Pleurocoryne* (Fig. 158) is also multilu- lar, but more variable in structure than the archegonium. It most commonly is a stalked body, the upper part being composed of an outer layer of sterile chlorophyll-bearing cells, and an inner mass of spermatozoa. Within all of these cells a protoplasmic zoid is developed. The body of the spermatoid is derived mainly
+
+![]() A B C D E F.
+Fig. 158.—*Pleurocoryne* ovata. Development of the archegonium. A-D, median longitudinal sections (× 650). E, an older one (× 320). F, spermatoid (× 900).
+
+from the nucleus of the sperm-cell, while the cilia arise from a special body, the Rhapho-plast, which, in its position, recalls the centrosomes of certain cells, but is found only in the later stages of the sperm-cells. Like the walls of the canal-cells of the archego- nium, this special body bursts open at maturity. When the ripe archegonium is wet, the swelling of this mucilaginous mass bursts open the archegonium and sets free the sperm-cells, from which the spermatoids are liberated by the complete dissolution of the cell-walls.
+
+The liberated spermatoids swim about actively in water and make their way to the open archegonium, to which they are attracted by substances ejected from it. This attractive substance in the Ferns is malic acid. The spermatoids often collect in large numbers about the mouth of the archegonium and several may make their
+
+198
+BOTANY
+
+way into it; but normally only a single one penetrates into the egg and fuses with its nucleus.
+The Embrya. — The fertilized egg does not form a resting-spore,
+
+![]() A. A section of the venter of a ripe archegonium (× 300). B-D, development of the embryo, seen in longitudinal section (× 300). E-F, transverse sections.
+
+Fig. 159. — *Tortopsis* *Appophylia*. *A*, section of the venter of a ripe archegonium (× 300). *B*-D, development of the embryo, seen in longitudinal section (× 300). *E*-F, transverse sections.
+
+but grows into a mass of tissue, the embryo (Fig. 159), which sooner or later develops into the sporophyte, the plant which gives rise to the non-sexual spores.
+
+THE ARCHEGONIATæ 190
+
+**Sporophyte.** — The sporophyte (Fig. 160) shows a very different degree of development among the Archegoniatæ. In its simplest form (e.g. Riccia) it is a globular body which is almost entirely composed of sporogenous tissue. In the Ferns, spore-production is largely confined to the vegetative exist-
+ence of the sporophyte, which becomes a large, leafy plant, and later the sporophyte develops a special spor-
+ogenous tissue, each cell of which divides into four parts (Fig. 161), pro-
+duces the spores, which are very similar in structure throughout the group. The sporogenous tissue (Arch-
+esporium) may be developed from the inner tissue of the sporophyte, or there may be a special organ, the sperangium, in which the
+spores are produced.
+
+**Spore-formation.** — The development of the spores among the Archegoniatæ is very uniform, and is one of the strongest proofs of a common origin for all of them. The sporogenous cells arise from a single cell by repeated divisions (Fig. 162). Each
+sporogenous cell contains a large nucleus which divides twice.
+The divisions may be followed at once by a division-wall, but more often the four daughter-nuclei lie free in the cytoplasm of the mother-
+cell. Division-walls are then formed between these nuclei,
+which are rounded or somewhat tetrahedral in form. The
+ripe spores usually contain a large amount of starch, oil, or albumi-
+nous reserve-food, and are protected by a heavy outer spore-coat, or Perithelium (Fig. 163), which is sometimes perforated.
+
+**Reduction of Chromosomes.** — It has been ascertained that, in some cases at least (e.g. *Osmunda regalis*, *Polypodium decipiens*), the num-
+ber of chromosomes in the nuclei of the sporophyte is double that
+of the gametophytic nuclei. The reduction takes place in the last
+division of the archesporial cells, which results in the spore mother-
+cells.
+
+![]() A
+![]() B
+![]() C
+
+Fig. 160. A. Sphaerocarpus cruciatus; median sec-
+tion of mature sporophyte (* × 220*). The archesporial
+cells constitute the archesporium; f, foot. B, C.
+Ferns; sporophyte; two ripe spores, E, and an
+elater, C (* × 250*).
+
+f
+
+300
+BOTANY
+
+The germinating spores produce in turn the gametophyte. The latter, in abnormal cases, may arise as a direct outgrowth of the sporophyte (Apospory), and conversely the sporophyte may develop as a vegetative growth from the gametophyte (Pogamy).
+
+THE MUSCINEE (BRYOPHYTTA)
+
+The Archegonates fall into two series of equal rank, the Bryophytes or Mosses in a wider sense, and the Pteridophytes or Ferns and their allies.
+In the former group, the gametophyte is the pre-dominant phase; in the latter, the sporophyte which becomes an independent, long-lived plant.
+
+The Liverworts are usually divided into two classes, Liver-worts (Marchantia) and Mosses (Musci). It seems best, however, to add a third class, Anthocerotales, to include certain forms which have been united with some extent, intermediate in character between Bryophytes and Pteridophytes.
+
+Gametophytes. - The gametophytes of the Marchantiaceae are a delicate thallus, not essentially different from that of some Algae, or it may be highly differentiated, showing well-developed stem and leaves, as is seen in the higher Mosses. These structures differ, however, from those of other parts of the sporophyte of the vascular plants (Ferns and Seed-plants).
+
+The Sporophyte. - The simplest sporophyte is that of Riccia, which consists of a globular body, all of whose cells, except a single superficial layer, produce spores. In all other Bryophytes a greater or smaller part of the sporophytic tissue is sterile, and is connected with
+
+![]() A: A sporangium showing a young spore within.
+![]() B: A section of a ripe spore.
+![]() C: Section of a ripe spore.
+![]() D: Surface view of the epispore.
+
+Fig. 161. - Riccia flabellata. A. sporogenous cell under- going division to produce daughter cells. B. section of young spore-intestine (× 300). C. section of a ripe spore. D. surface view of the epispore.
+
+The Anthocerotales are, to mediate in character between Bryophytes and Pteridophytes.
+
+301
+
+THE ARCHEGONIATE
+301
+
+the vegetative existence of the sporophyte itself. In the more specialized forms like the True Mosses and Anthoceros, spore-formation is subordinated, and the sporophyte develops green assimilative tissues only during its early stages, and is dependent upon the gametophyte only for its supply of water.
+
+**Biology.** — The Bryophytes are, for the most part, inhabitants of moist localities, and a few are true aquatics (e.g. *Riccia fluitans*, *Fontinalis*). *Tussilago farfara* is found in the earth and moist rocks, banks of trees, and similar places. They have become by adapted to a dry situation, and become completely dried up without injury. This is strikingly shown by many Californian Bryophytes, which remain dormant through the long rainless summers, resuming
+
+![]()
+A small illustration showing a plant with a central stem and two lateral branches.
+
+
+Fig. 165.—Tussilago farfara. Germination of spores (× about 200). C, E, optical sections; x, apical cell; r, primary rhizoid; sp., spore-membrane.
+
+growth at once with the advent of the autumn rains, and completing their season's growth during the rainy winter.
+
+Live mosses are often the most conspicuous features to constitute a con-
+spicuous feature of the flora, but the Mosses are often gregarious,
+and in the wet northern regions often cover large tracts, almost to
+the exclusion of other vegetation. This is seen especially in north-
+ern bogs, where the Mosses (Sphagnum) and Hygrohypnum, Polytrichum,
+etc., are the most important factors in the vegetation. In the
+northern forests, also, the ground and the decaying trunks of
+the fallen trees are covered with dense cushions of large Mosses.
+Similar conditions prevail in the cooler regions of the southern hemisphere.
+
+301
+
+202
+BOTANY
+
+**Class I. Hepaticae**
+
+The lowest of the Archegoniatae are the Hepaticae, or Liverworts, which are of importance, botanically, because they probably represent the forms from which all the higher types of green plants have come. They are usually of small size, and most of them frequent moist, shaded localities, but some of them occur in arid regions, and even in deserts. They reach their greatest development in the moist mountain forests of the Tropics, where they occur in great numbers upon the stems, or even the leaves, of many trees and shrubs.
+
+**The Gametophyte**
+
+The gametophyte in the Liverworts shows considerable range of structure. The simplest forms have a thallus composed of nearly uniform cells, or with a midrib consisting of elongated cells (Fig. 172 B).
+
+The branching is most commonly dichotomous, but in some cases it is reduced to the substratum by delicate unicellular root-hairs. The growth of the thallus is due both to divisions of a single apical cell (Fig. 163 A), and to the production of new cells in the earlier stages, conform to this type.
+
+From this simple thallose structure, specialization has developed in two directions. In one line, the thallose form has been retained, but the uniform tissues of the simpler type have been replaced by tissues more differentiated into leafy shoots and stem-like bodies. These green cells occupy the dorsal part of the thallus, and constitute a well-developed assimilating apparatus, and the reproductive organs are often restricted to special branches.
+
+The second line of development is seen in the leafy Liverworts, or Scale Mosses. The tissues in this type remain alike, but the plant-body becomes a leafy axis, the assimilative function being relegated to the leafy shoots. The leafy shoots sometimes arise as outgrowths of a thallose "Protonema," like that found in the True Mosses. This protonema may be a flat thallus (Lepidium meteoregum) (Fig. 180), or it may be filamentous (Protonema).
+
+**Reproduction.** The gametophyte multiplies normally by branching, but in many Liverwort special buds or gemmae are developed. In Aneura multifida, these are two-celled bodies, which are formed inside a mother-cell, and are discharged much like the zoospores of Prototheca.
+
+![]() A B
+
+Fig. 163. — *Ricciocarpus natans.*
+A, floating form.
+B, terrestrial form (cf. 57).
+
+163
+
+THE ARCHEGONIATE.
+203
+
+the Green Algae. They may properly be considered as homologous with zoospores. In other cases the gemmae are developed super-
+ficially, and break off from the thallus. In Marchantia (Fig. 169)
+and Lunularia (Fig. 170) the gemmae are produced by the
+archegonium.
+
+The Archegonium.—The sexual organs may be borne upon the
+same plant, or the plants may be unisexual.
+
+The development of the archegonium (Fig. 165) is remarkably uniform in all the higher plants, arising from a superficial cell which usually, but not always, divides by a transverse wall into a stalk-cell and an upper cell. The latter divides by three intersecting vertical walls, with a central cell and three peripheral ones. These peripheral cells divide by longitudinal walls, so that the central cell becomes surrounded by six peripheral ones. In the Jungermanniales, this longitudinal division is usually suppressed in the case of the smallest primary peripheral cell, so that there are but five of these in the archegonium.
+
+The next division is transverse and divides the young archegonium into two tiers, the upper giving rise to the neck, the lower one to the venter. From the axial cell of the neck a cover-cell is cut off, which now divides by internal transverse walls into two neck-canal cells. Repeated transverse divisions take place in all the neck-cells, so that the neck rapidly increases in length. The axial row of cells con-
+stitute the neck-canal cells. The axial cell of the venter divides once transversely into two neck-canal cells. The lower becomes the egg, the upper the central canal-lap.
+
+At maturity the transverse walls of the neck-canal cells become mucilaginous, and dissolve when the ripe archegonium absorbs water. The protoplasmic egg-cell contains a large nucleus and a few chloro-
+phyll granules. The topmost is usually darkly granular, except at the top,
+where a more or less evident clear "receptive spot" can usually be made out.
+
+The neck-cells become strongly distended by the water absorbed,
+and the pressure exerted by the swelling mucilaginous mass formed
+from the disorganized canal-cells finally becomes so great, that the apex of the neck is ruptured, and the contents of the canal are forced out, leaving behind only a thin layer of mucilage, down to the central cavity of the venter in which the egg lies.
+
+The Antheridium.—The antheridium (Fig. 166) shows much more variation than the archegonium. With the exception of the Antho-
+cerocales, it is developed by a single cell which divides internally directly into a basal and a terminal cell. The latter develops a
+mass of central sperm-cells, surrounded by a layer of larger sterile
+cells, which often contain chlorophyll. The nucleus of the sperma-
+cell is relatively large, and assumes a spiral form as the spermatoid
+develops. The two long cells always found in the spermatoids of
+
+304
+BOTANY
+
+the Bryophytes arise from the blepharoplast, which is of cytoplasmic origin. When the spermatonsia escape, the remaining cytoplasm of the mother-cell becomes the end, as a small vesicle.
+
+The wall of the sporophyte is thin at maturity, and the dehiscence of the antheridium is due to the swelling of this mucilaginous matter, when water is applied.
+
+**Sporophyte**
+
+The fertilized egg becomes at once invested with a cellulose membrane, and grows until it completely fills the cavity of the vesicle. The development of the sporophyte in the Liverworts is not always the same. In the simplest type, that of Riccia (Fig. 171), all but a single superficial layer of cells constitutes the archesporium of the globular spore. This all-mucilaginous mass gives rise to sporocytes. In all other forms there are one or more smaller or larger masses of sterile tissue in the sporophyte. In the Anthocerotales, especially the genus Anthoceros, the sporophyte becomes very complicated. A distinct antheridium grows out from within, with stomata, is developed, and the archegonium is relatively small.
+
+As the embryo grows, the venter of the archegonium also shows active growth, and, except in the Anthocerotales, the sporophyte is retained within it. Within this of the archegonium is found a "Calyptra," just the spores or "spores." Thus by a sudden elongation of the stalk, or "Seta," of the sporophyte, it breaks through the calyptra, and carries up the spore-bearing capsule at the top, soon shedding its contents.
+
+In most of the Liverworts certain cells of the archesporium remain undivided, and develop into spindle-shaped cells, upon whose walls are developed spiral thickeninges, which are strongly hygroscopic. These cells are called "Calyptids" (Fig. 169, C), and it is probable that they are of assistance in breaking through the calyptra. The spores themselves, and possibly the hygroscopic movements may also be useful in sealering the spores after they are shed. The wall of the capsule, or upper-spore-bearing portion of the sporophyte often shows similar thickening on its outer walls, and these also increase in thickness in covering the capsule.
+
+In all Liverworts except the Ricciaceae, the base of the sporophyte forms a bulb-like organ, the Foot (Fig. 169, A'), whose cells are in close contact with the adjacent cells of the gametophyte, from which it absorbs water and food for the needs of the growing sporophyte, which is thus parasitic, as it were, upon the gametophyte.
+
+The Spores. The ripe spores of the Liverworts are tetrahedral cells with both or one polar cap opening outward. Where the spores can germinate at once, as in most forms from the moist
+
+THE ARCHEGONIATE 205
+
+tropical forests, the spores contain chlorophyll; but where the spores are adapted to endure a long period of drought, as in most Californian species, the ripe spores contain no chlorophyll, but are withered, withered, and brown. The spores of some species have much heavier walls, also, than those which contain chlorophyll.
+
+*Hemionites.*—Where chlorophyll is absent from the ripe spores, the first sign in germination is the appearance of chlorophyll in the spore, although the amount is sometimes small. The exospore and perinum are ruptured (Fig. 162), and the spore-contents, included within the endosporium, or intine, appear as a vacuilla, the germ-tube, which often at first appears elongated. Upon the formation of this germ-tube a small papilla is cut off, which rapidly elongates into the primary rhizoid.
+
+At the end of the gametophytic mass of cells is developed, which soon becomes a thallus-like, growing from a definite apical cell. This apical cell, in most cases, is of the two-sided type, found persistently in Metzgeria and Aneura. Sooner or later, this is replaced by the type found in the mature gametophyte. With few exceptions, the young plant assumes gradually the characters of the adult.
+
+**Classification of Hepaticae**
+
+The Hepaticae (exclusive of the Anthocerotales) may be divided into two orders, the Marchantiales and the Jungenmanniales. The gametophyte in the former is always thallose, and may become very complex; in the latter, it may be either thallose or foliose, but always is relatively simple in its cellular structure.
+
+Order I. *Marchantiales*
+
+These very characteristic plants possess a prostrate, fleshy thallus (Figs. 163, 164), which usually grows upon the earth, to which it is attached by numerous root-hairs of two kinds,—large, thin-walled ones, and smaller hairs, with tubular walls, having peculiar spike-like thickening near their inner ends. In many species these roots are adventitious.
+
+The branching of the thallus is usually dichotomous, but adventitious shoots are common in many forms. With the exception of the tropical genera *Dimerocarpus* and *Dimerocarpon*, in which the nature of the thallus is poorly marked, the Marchantiales show two definite regions of the thallus (Fig. 167), a central portion, composed of compact, colourless tissue, sometimes containing special mucilage-cells, or ducts, and cells with oil-bodies; and an outer region which may merge with or be separated from the vascular tissues composed of green cells, with large air-chambers, or lacuna. These chambers
+
+306
+BOTANY
+
+communicate with the air outside by means of pores, which, in the higher Marchantiaceae, may have the form of chimney-shaped stomata.
+
+![]() A
+![]() B
+![]() C
+
+![]() D
+![]() E
+
+sp
+pnr
+st.
+ar.
+r
+
+Fig. 164. — *Fimbriaria* (Hypnum) *Californica*. *A*, plant with two sporangial receptacles, slightly enlarged. *B*, a receptacle (carposporophore) (*x 8*). *C*, the same cut transversely, showing the spores. *D*, young carposporophore, in longitudinal section, showing one of the growing-points. *E*, growing-point and archeogonium (*x 30*).
+
+The air-chambers may be clearly defined, each with a single stoma, and, in such cases, the upper surface of the thallus presents a regu-
+
+307
+
+THE ARCHEGONIATE.
+207
+
+Early marked areolation, as in Marchantia and Conocephalus (Fega-
+telis).
+Upon the lower surface of the thallus are usually two series of
+delicate scales, often of a dark purple color. These sometimes are
+provided with a glandular tip, which secretes a mucilaginous sub-
+stance, and they are doubtless protective in their function, closely
+investing the delicate growing apex of the shoot.
+
+![]()
+A. Longitudinal section of the apex of the thallus, with
+young sporangium at the base.
+B. Transverse section of the same.
+C. Diagram showing the arrangement of the
+primary divisions in the archegonium.
+D. Diagram showing the arrangement of the
+primary divisions in the archegonium.
+E. Diagram showing the arrangement of the
+primary divisions in the archegonium.
+F. Diagram showing the arrangement of the
+primary divisions in the archegonium.
+G. Diagram showing the arrangement of the
+primary divisions in the archegonium.
+L. Diagram showing the arrangement of the
+primary divisions in the archegonium.
+
+
+Fig. 163. -- Riccia pilosa.
+a. Longitudinal section of the apex of the thallus, with
+young sporangium at the base.
+b. Transverse section of the same.
+c. Diagram showing the arrangement of the
+primary divisions in the archegonium.
+d. Diagram showing the arrangement of the
+primary divisions in the archegonium.
+e. Diagram showing the arrangement of the
+primary divisions in the archegonium.
+f. Diagram showing the arrangement of the
+primary divisions in the archegonium.
+g. Diagram showing the arrangement of the
+primary divisions in the archegonium.
+l. Diagram showing the arrangement of the
+primary divisions in the archegonium.
+
+Classification of Marchantiales
+
+The Marchantiales may be divided into three suborders -- Ricci-
+cea, Corsiniaeae, and Marchantiaceae.
+
+Suborder I. Ricciacea
+
+The lowest of the order are the Ricciaceae, containing the two
+genera, Riccia and Ricciocarpus (Fig. 163). Most of them are ter-
+restrial forms, but Ricciocarpus and Riccia fluitans are genuine
+aquatic plants.
+
+Apical Growth.--The thallus grows from an apical cell (or possibly more than one), which is wedge-shaped, with segments cut off alternately from the dorsal and ventral sides by transverse walls on both lateral faces. The greater part of the thallus is derived from these developing segments;
+ventral segments develop only the lower epidermis, from which the root-hairs
+
+Suborder II. Corsiniaeae
+
+The Corsiniaeae include two genera, Corsonia and Corsoniastrum,
+which are aquatic plants, but Corsonia is terrestrial and Corsoniastrum
+aquatic. The thalli are very similar to those of Ricciaceae, but differ in that
+
+208
+BOTANY
+
+grow, and the overlapping lamellae, which are formed by the rapid growth of the free margin of the segments, and curve upward over the apex. These lamellae are very inconspicuous in certain species (e.g., *H. plasmo*), while in others they may be well developed, split in the middle, and form two rows of scales like those of the Marchantiales.
+
+The dorsal segments grow much more rapidly, and divisions occur in all directions, so that the cells become elongated, and the air-spaces become more or less definite vertical rows, which separate at an early period, and give rise to narrow air-spaces between them. The air-spaces are large, and extend throughout the air-spaces between much larger, and approach the condition found in the Marchantiales.
+
+The green cells are thus brought into direct contact with air containing oxygen, and this is probably one of the causes of the rapid development of such a usually colourless, and somewhat enlarged, so that a sort of epidermis is developed. Differences in the size of these cells probably regulate, to some extent, the rate of respiration, and thus help to keep the plant healthy outside.
+
+In Ricciocarpos, where the air-spaces are large, there is a definite epidermis with pores like those of the higher Marchantiales.
+
+![]() A. B. C. D.
+
+Fig. 165. — *Fimbriaria sp.* A. part of a vertical section of a young anthoceratid receptacle, showing two very young anthocerata B. C-E. elder stages of the anthocerata (x 30).
+
+**Sex-organ** The sexual organs of Riccia (Fig. 165) are borne upon the dorsal surface of the thallus, but owing to the growth of the tissue about them, they are surrounded by an envelope, which, in the case of the anthoceratum, extends upwards to cover almost its whole length. The cells composing each anthoceratum arise from similar superficial cells, and closely resemble each other at first. The development of the archegonium conforms to the regular type. At maturity it is a simple structure.
+
+The anthoceratum, after a short basal cell is cut off, divides by a series of transverse divisions which are followed in each of the segments by two intersecting internal walls. A peripheral wall then forms between these segments a central cell from a peripheral one. The central cell, thus produced by further transverse divisions, becomes a stalked egg-cell. The embryo.—The globular egg divides first by a transverse wall, and then undergoes quadrant and octant divisions by walls passing through its centre (Fig. 171). After this it is cut off by another transverse wall which passes to cut off, and all the central mass of cells become the archesporium, all of whose cells develop spores. The outer storile cells become more or less completely
+
+THE ARCHEGONIATE 209
+
+destroyed as the spores mature, and they then lie free in the venter of the archegonium, which has kept pace with the growth of the embryo and has become two-layered.
+
+A.
+![]() A diagram showing a longitudinal section of the thallus, with the archegonia, ar., and ventral scales, v., (× 100). B. section through a pore, showing the chlorophyllous cells, cl., of the air-chamber (× 300).
+
+Fig. 387. — *Floridopsis hypogylia*. A. longitudinal section of the thallus, showing the archegonia, ar., and ventral scales, v., (× 100). B. section through a pore, showing the chlorophyllous cells, cl., of the air-chamber (× 300).
+
+**Suborder II. Corsinaceae**
+
+This is a small group intermediate in character between the Ricciaceae and the Marchantiaceae. The thalli are generally simple, and differ from the Ricciaceae in having the lower part of the embryo developed into a foot, and some of the archesporial cells remain sterile, and form rudimentary clusters. There are two genera, *Corsinia* and *Fusilicaria* (Bouché).
+
+**Suborder III. The Marchantiaceae**
+
+The Marchantiaceae, with the exception of the aberrant genera *Dumortiera* and *Monoclea*, have the assimilative tissue of the thallus sharply differentiated.
+
+210 BOTANY
+
+from the ventral tissue. The air-chambers may be irregular, or they may be clearly demarcated, and visible to the naked eye as polygonal vacuolations upon the dorsal surface of the plant. These chambers may be openings surrounded by radiating epidermal cells, or there may be a definite central cavity, resembling in some respects the interior of a chimney-like series of superimposed chambers. In the lower one such an opening is visible, but the upper ones are not. The stoma is especially well developed upon the ventro-ventral receptacles (Fig. 168).
+
+A.
+
+B.
+
+C.
+
+Fig. 168.—Pleurobrachia Californica. A-C, development of the pores upon the receptacle, longitudinal section. D, surface view of a pore.
+
+In special cases, and usually during, occur in some species.
+
+Genus Riciana.—Gemmae of a peculiar type (Fig. 169) occur in Marchantia and Lunularia. They are flattened buds which are borne in large numbers in special receptacles on the ventral side of the plant. Each bud arises from single epidermal cells, which divide transversely into a short basal cell which remains undivided, and a terminal cell which by repeated divisions gives rise to the body of the bud. The body is usually cup-shaped at each edge, so that it is fiddle-shaped. These indentations mark two growing-points, and when the bud falls upon the earth they grow out in opposite directions into two shoots. The shoot tips are covered with a thin cuticle secreted by small glandular hairs growing with them. Both surfaces of the bud are alike, and both buds fall down together. The lower part of the bud is always in contact with the ground. Whatever surface of the bud falls downward becomes the ventral surface of the young plant, and the upper surface develops into a shoot.
+
+Sex-organ.—The sexual organs, which closely resemble those of Riccia, are borne in groups upon more or less modified parts of the thallus. The plants are either monoecious or dioecious. In Riccia, the sex-organ is situated upon the dorsal surface of an ordinary shoot, as in Fimbriaria (Hypnocentrum), or there may be several peripheral branches, as in Tagnotria and Marchantia (Fig. 169).
+
+The archegonia are always borne upon more or less modified shoots, which may consist of a single branch or a system of short branches (Fig. 169). They are familiar in Marchantia and other genera. These receptacles may represent a single branch, or they may be composed of a system of short branches.
+
+THE ARCHEGONIATE.
+211
+
+The Sporophyte
+
+As in Riccia, the first division in the fertilized egg is transverse; but only the upper half of the embryo gives rise to sporophytes. In this case, the proximal half developing into a short stalk, and the more lower end forms a foot, which is buried in the neck of the gametophyte (Fig. 107).
+
+The upper part of the sporophyte, the capsule, is a thin-walled compound usually of a single persistent layer of cuticle. The wall may develop thickenings upon their inner surface.
+
+The rest of the capsule is composed of the archesporium, some of whose cells develop into well-marked elaters, the others becoming mere vacuoles in the usual way.
+
+The dehiscence of the capsule may be irregular, or there may be a lid formed, which falls away when the spores are ripe.
+
+The Marchantiales comprise the most conspicuous of the Hepaticae, such genera as Marchantia, Conocephalus, and Lunularia being among the best-known forms.
+
+Order II. Jungermanniales
+
+The majority of the Hepaticae belong to the Jungermanniales, which are especially abundant in the moist forests of the Tropics. Most of them are epiphytic and can be found on the bark of trees in every wood, although a few --e.g. Biasia, Fossombronia--occur upon the ground. The gametophyte in the lower forms is a simple thallus, but the greater number are leafy forms--the so-called "Scale Mosses." With very few exceptions, the gametophyte is markedly dorsiventral in structure.
+
+![]()
+A. A.
+B. B.
+C. C.
+D. D.
+E. E.
+F. F.
+G. G.
+
+
+Fig. 107.--Marchantia polymorpha.--A plant with gemma-cupe (natural size). B.--F., development of the gemma-cupe (natural size). C.--F., showing two growing-points, v', v" (× 300).
+
+
+5
+
+212
+BOTANY
+
+The Jungermanniales are divided into two suborders, the Anacrogynae, or Metzgeriaceae, and the Aerogynae, or leafy Jungermanniaceae. In the former, the archegonia are dorsal, and never arise directly from the apex of the shoot; in the Aerogynae, the apex of the arche- gonial shoot becomes transformed into an archo- gonium, and its longitudinal growth is thus stopped.
+
+Suborder I. J. Anacrogynae
+
+The anacrogynous Jungermanniales are of especial interest, as they represent, on the whole, the simplest type of the Archegoniates, and one suggesting the ancestral form from which all other types have been derived. Among the Anacrogynae are many interesting transitional types. The lowest forms have a delicate shoot growing from a bulbous and often coiled, and closely resembling the younger stages of many of the Arche- goniae, which may be traced back to such a form. The early stages of such Liverworts as the Marchantiacae, and the young gametophyte of most Ferns, usually conform to this type. Some of
+
+![]() D.
+![]() A.
+![]() B.
+![]() C.
+
+Fig. 171. - A-C. Riccia glauca. D. R. trichocarpa. A, B. longitudinal. C. transverse sections of young embryo (× 300). D, an older embryo, showing the layer of sterile cells, m, surrounding the sporogenous cells (× 250).
+
+Fig. 172. - A-C. Riccia glauca. D. R. trichocarpa. A, B. longitudinal. C. transverse sections of young embryo (× 300). D, an older embryo, showing the layer of sterile cells, m, surrounding the sporogenous cells (× 250).
+
+THE ARCHEGONIATE.
+215
+
+the Anacrogynae, like Blasia and Symphyogyna (Fig. 172, E), show a development of rudimentary leaves, or special assimilatory organs, like those which characterize the more specialized Acrogynae.
+
+Anacrogynes. - The simplest of the Anacrogynes are the Anacrales, inter-
+mediate in structure between the typical Acrogynes and the plants which they resemble somewhat in the rate of growth of the thallus and the char-
+acter of the sexual organs. The genus Sphaerocarpos (Fig. 190) is, on the whole, the lowest of this group, but it is not so low as to be identical with the other genera. The Anacrales are so called because the sterile archegonial cells do not develop into perfect elaters, but remain as oval, thin-walled cells, usually containing starch and some chlorophyll.
+
+![]() A B C D E F
+Fig. 172. — A. *Asura* (Riccardia) pinnatifida (× 4). B. *Pellia* crenulata (× 3). C, D. *Fissidens* longifolia (× 3); sp., sporophyte. E, *Symphyogyna*, sp. (× 3). F, *Acrogynum* incertum. P., *Pellia* incerta (× 3).
+
+The typical Anacrogyne (e.g. Pellia, Asura, Fissidens) is represented by a plant which has a simple thallus upon the dorsal surface of the thallus, or that of special branches. The archegonium is much like that of the Marchantiales, but except in the lowest forms, there are but five peripheral cells only in the upper part of the archegonium, and these are very small and agree less with that of the Acrogyne. The first division-wall in the upper part of the archegonium separates two central cells from three peripheral ones; the next divisions separate a central cell from three peripheral ones, so that the
+archegonium consists of two central cells which subsequently give rise to the spermatozoa and six peripheral cells which produce the egg. The gametangia are relatively larger, and coiled several times. At the anterior end are two very long cilia.
+
+The root-hairs of the Jungermanniales are always of the simple type, and the scales found upon the ventral surface of the Marchan-
+tales are replaced in these forms by glandular hairs, which serve to protect the growing-point of the shoot.
+
+214
+BOTANY
+
+**Gemmae.** — In *Aurea multifida*, two-celled gemmae have been de-
+scribed, which escape from the cells of the thallus in a manner
+resembling that of zooids in the Green Algae, but in other
+genera—e., Rhizoclonium—cellular gemmules like those in
+Marchantia, are formed.
+
+**Tubera.** — In some Anacrogynous of dry regions, such as *Goodenia lobata*, there is developed toward the end of the growing season a
+subterranean tuber, which remains dormant during the dry season,
+and starts into growth again with the advent of the winter rains.
+
+![]() A horizontal section of young antheridial branch (× 300); z, apical cell; c, antheridium. B, transverse section of antheridial branch (× 300). C, young ripe archegonium (× 300). D, E spermatangia of *Polia* edulis (× 1250). (D, E after Gürzemann.)
+
+The **Sporophyte.** — The first division in the embryo is always transverse. In the Anacrogynous genera, the embryo is divided by a transverse furrow, but in the typical Jungermanniales the lower of the two primary cells remains undivided, or develops into a small appendage of the foot, and from the upper ("epibasal") cell are derived all the other parts. The following diagram shows three parts: the capsule, seta, and foot.
+The sporophyte is usually divided into four parts, but the division is in-
+dicated before the nucleus divides, in the form of four aculeate outgrowths of the
+cell, before any indication of division is shown by the nucleus. A "quadri-polar" spore is then developed, and the division-walls are formed between the four
+young spores.
+
+![]() A diagram showing the structure of a sporophyte. It shows three parts: the capsule, seta, and foot. The sporophyte is usually divided into four parts, but the division is indicated before the nucleus divides, in the form of four aculeate outgrowths of the cell.
+
+THE ARCHEGONIATE 215
+
+The sporophyte remains included within the calyptra until the spores are ripe, when there is a sudden elongation of the seta, which
+
+![]() A B C
+Fig. 174. — A, Anthera multifida. Young embryo, optical section (× 250). (After Laveran.) B, young embryo, showing the calyptra. C, upper part of B (× 300); g., spermatangia cells; e., young embryo; m., apical mass of sterile tissue.
+
+may increase many times in length within a few days, owing to the stretching of the walls, brought about by the consumption of the substances within the cells. In *Pellicia epiphylla*, the seta has been observed to increase from one millimeter to two millimeters in three or four days. This extraordinary growth is at the expense of starch which fills the cells of the young embryo. The capsules usually opens by four valves, but this is not always the case.
+
+Suborder II. Acrogynae
+
+The acrogynous Jungenmanniales comprise the larger number of the described species of Hepaticae, but the type is a much more fixed one than that of *Anacria*. Such foliose forms among the latter genus as Blasia, Fossombronia, and especially the peculiar genus Trebilia, are intermediate, to some extent, between the Anacrygonia and the Acrogynae; but the num-
+
+![]() Fig. 175. — Monotheca Bolanderi. A, female; R, male; plantæ (× 4); V, longitudinal branch; S, umbellular branch.
+216
+
+216
+BOTANY
+
+bers of the latter group conform invariably to a single structural type. The apex of the shoot (Fig. 176) is occupied by a single apical cell only, except in the genus *Phyllostachys*, is transversal in form. In transverse section it appears as a triangle, which is usually isosceles, with the shorter side turned toward the ventral surface of the shoot. There are three series of segments formed, corresponding to the three lateral faces of the apical cell, and each
+
+![]() A. A longitudinal section of a vegetative shoot (800); d, dorsal; v, ventral surface.
+![]() B. A longitudinal section of an antheridium; x, of archegonial shoot; c, mother-cell of antheridium; f, young archegonium.
+![]() C. A longitudinal section of an antheridium; x, of archegonial shoot; c, mother-cell of antheridium; f, young archegonium.
+![]() D. A longitudinal section of an antheridium; x, of archegonial shoot; c, mother-cell of antheridium; f, young archegonium.
+
+Fig. 176. — *Mastixia Bolanderi.* A, longitudinal; B, transverse, section of a vegetative shoot (800); d, dorsal; v, ventral surface. C, longitudinal section of an antheridium; x, of archegonial shoot; c, mother-cell of antheridium; f, young archegonium.
+
+segment gives rise to a leaf, except where the ventral face of the apical cell is very narrow, in which case the ventral series of leaves, the “Amphigastria,” are not developed.
+
+The fully developed shoot shows a definite central axis, upon which the leaves are arranged in three rows, two dorsal and one ven-
+tral. The leaves are usually alternate and opposite. They are either of equal size, or, more commonly, the upper lobe is larger, and over-
+laps the lower lobe of the leaf in front of it. The leaves and stem
+
+THE ARCHEGONIATE
+217
+
+are composed of almost perfectly uniform, green parenchyma, and no
+tree of a midrib
+is ever found in
+the leaves.
+
+The lower lobe of the dorsal leaves, commonly in many of the epiphytic tropical species of Monocle-
+nia,becomes folded over so as to form
+a little sac (Fig.
+181), which is ap-
+parently used in
+storing water. It
+is said that in some
+instances these
+sacs serve to trap small crusta-
+ceans or insects, acting like the
+traps used upon the leaves of Utri-
+cularia.
+
+Branching. - The branching in the Acrogynum is always monopodial. The
+lateral branch replaces the lower lobe of a leaf. In the ventral half of the
+
+![]()
+A-D. Longitudinal sections of successive stages in the development of the young antheridium, longitudinal sec-
+tions (× 300).
+
+
+Figs. 177. - *Monoclea Bolanderi.* Development of the embryo. A-D. Longitudinal sections of successive stages in the development of an embryo. E and F are successive longitudinal sections of the same embryo (× 300).
+
+![]()
+E-F. Successive longitudinal sections of the young antheridium (× 300).
+
+
+218
+BOTANY
+
+young leaf, which would ordinarily develop into its lower lobe, intersecting walls arise which cut out a tetrahedral cell, at once transforming it into the apical cell for the new shoot.
+
+**Reproduction**
+
+*Gemmae.* — Unicellular or biconical gemmae are found in many forms, and usually arise from marginal cells of the leaves, falling off with the leaf, resembling much as the spores do. Less commonly, *Lepidium contortum*, *Lepidium periparus*, multicellular gemmae are produced.
+
+Sex-organ.
+The thallus may be either monocious or dioecious. In the lat-
+erally compressed common genus *Ma-
+dotheca* (Bellini,
+Schultze, 1753), the reproductive
+branch is some-
+what different from the sterioi ones. The antheridia (Fig. 171) are borne singly in the axis of closely
+branched axes, upon short lateral branches. The anthe-
+ridium is large and broad in its development
+with that of the ana-
+crygonum, but is often long-stalked, and in *Madotheca* is the lower part of the wall more massive than in the other genera.
+
+**Archegonium.** — The archegonia are formed by segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axial cell (176 D), which are elongated and arise from segments of the axi
+![]() A diagram showing a longitudinal section through a plant embryo.
+A. B. C. D. E. F. G. H. I. J. K. L. M. N. O. P. Q. R. S. T. U. V. W. X. Y. Z.
+
+Fig. 170.— *Modothea Bolanderi*. A, nearly median longi-
+tudinal section of an advanced embryo ($x$ 300). B, upper part of the same ($x$ 500). C, sporophytic cells and young gametophytes ($x$ 500).
+
+The development of the sporophyte in the Arachegonium is very much like that of the lower Jungerrnanillaeans. Here, also, the whole of the sporophyte, except
+
+THE ARCHEGONIATAE 219
+
+the small appendage at the base, arises from the epibasal half of the two-celled embryo.
+
+**Classification of the Acrogynes**
+
+The division of the Acrogynes into separate families offers some difficulties, as the group is a very large one, containing comparatively few marked differences. The following families have been proposed:
+
+I. Epigoniantheae;
+II. Trigonanthae;
+III. Pithanthae;
+IV. Scapanioideae ;
+V. Stephaninoideae;
+VI. Pleurozoideae;
+VII. Bellininoideae;
+VIII. Jubuloideae.
+
+**Class II. ANTHOCEROTALES**
+
+The Anthocerotales include three genera which agree closely among themselves, but are so different from the other bryophytes, with which they are usually associated, that it seems best to separate them from the rest, and to coordinate with the whole of the Hepaticae.
+
+Fig. 180.— *Lejeunea trapezifolia*. A, thallus proto-
+nema with terminal leaf buds, b (× 14). B, gem-
+mae of *Cobbernea* *Gmelinii.* (After Gmelin.)
+
+The gametophyte (Fig. 182) is a simple thallus in most species, but in *Lejeunea* and *Cobbernea* it is modified by secondary leaf-formation, not unlike that of *Fossombronia.* In this genus, the thallus has a definite midrib, while the rest of the thallus is but one cell thick. In the other genera, Anthoceros and Notophylax, the thallus is flattened and leafless. *Dendroceros* is a tropical genus, and is epiphytic in its habitat. The other genera occur also in temperate regions and are terrestrial.
+
+![]() A diagram showing the structure of a thallus with terminal leaf buds.
+A.
+b.
+h.
+
+![]() A diagram showing a thallus with gemmae.
+B.
+h.
+a.
+b.
+a.
+
+220
+BOTANY
+
+Cell-structure. — All Anthocerotales agree in the structure of the thallus.
+The apical growth is similar to that in the lower Jungermanniales, but a peculiar-
+larity is the presence of a single chromatophore, which is very rare, so that
+many of the Confermata, like Catenula, and Chatothecum, upon the lower side of the
+thallus, are without this organ. The cells of the thallus, by simple root-hairs, are stoma-like clefts,
+which communicate with cavities filled with mucilage. The cells of the paraphysoid filaments of Nostoc enter the thallus and establish themselves there. These endo-
+phytic Nostoc-like organisms possess features in all species of Anthocerotales.
+
+Reproduction
+
+The reproductive organs are formed together on the upper surface of the
+thallus much as in Riccia, but they differ in certain respects from those of the true
+Hyphothecium, and most rather those of the lower Pteridophyta.
+
+Anthocerium. — The anthocerium (Fig.
+165) is a superficial cell divided by a transverse wall into an outer and an inner cell, of which the latter may divide further, so as to produce a group of
+lower leaf-buds, z, modified into
+water-sprouts. In some species of Dendrocerus becomes more complex, and is com-
+posed of a single layer of cells, each containing a chromatophore, which often
+assumes a red or yellow color at maturity.
+
+Arthropodium. — The outer-cell does not project above the
+surface of the thallus, and it remains very inconspicuous, the outer neck-cells
+not being clearly distinguishable from the adjacent thallus-cells, and the egg-
+cell being some distance below the level of the thallus, as is the case in the
+Ferns.
+
+The Sporephyte
+
+The sporephyte in the Anthocerotales differs very much from
+that of the Hepaticae. The archesporium, or sporogenous tissue,
+is reduced to a single primary layer of cells, which later divides into two, or in Notothyrius into four.
+
+The first divisions in the embryo (Fig. 165) result in several tiers of cells,
+which become next divided by periclinal walls into a central part, or "the Endo-
+chromium," and an outer part. In A. Aurantiacum these take no part in spore-formation, but persists as a central strand of tissue, the colu-
+
+![]() A diagram showing a cross-section of a thallus with various parts labeled: A - Thallus; B - Reproduction; am - Antheridium; x - Xylem.
+
+Fig. 165. A. Lepidium sp., showing the ventral leaves or antheri-
+gastria, om (x about 40). B. Wartia sp., showing the lower leaf-bud z,
+modified into water-sprout (x about 40).
+
+X - Xylem
+
+THE ARCHEGONIATE.
+221
+
+mulla, which in position suggests the primary vascular bundles of the Fern-embryo. From the amphitheacum, by a second series of periclinal, there is separated on its inner side a layer of cells which forms the archesporium.
+
+The large sporophyte is attached to the base of the embryo of the Hepaticae; but between the foot and the upper part of the embryo there is developed a zone of actively dividing cells, which cause the sporophyte to elongate rapidly, so that it becomes much larger than the embryo where the sporophyte never assumes a large size; but in some species of Antho-
+cerus it continues for several months—indeed, as long as the gametophyte remains attached to the sporophyte. The sporophyte is usually less than two to eight centimetres. These large sporophytes have a well-developed assimilative tissue system, several layers of the outer cells forming a spongy green parenchyma, closely resembling that of the leaves of higher plants. It is very similar in structure to those of the leaves of the higher plants. Were the sporophyte put into communication with the earth by the development of a root, it would be quite independent of the gametophyte.
+
+The archesporium shows a more or less evident separation into fertile and sterile portions, which suggest a condition something like the formation of sporangia in the simplest Ferns. The sterile cells in some cases develop into elaters, but these differ somewhat from those of the Hepaticae.
+
+![]()
+A D
+B C
+sp E
+
+
+Fig. 132.—A-C, Anthoceros uniformis. A, gametophyte with four sporophytes attached (× 2). B, upper part of foot of one sporophyte, discharging spores. C, base of sporophyte surrounded by the calyptrae, or sheath (× 10). D, Sphaero-
+cevus junciformis, enlarged. (After Lacroix.) E, Nothocleis orbicularis (× 6).
+
+
+222
+BOTANY
+
+![]() A. Apex of thallus and archegonium (× 600); z, the apical cell.
+
+![]() B. C. D. E.
+
+**Fig. 183.** — *Nototrichia orbicularis*. Apex of thallus and archegonium (× 600).
+
+![]() Fra. 184. — Nototrichia orbicularis. Development of the antheridium. D, cross-section, the others longitudinal sections. A-D, × 600. E, × 300.
+
+THE ARCHEGONIATE 225
+
+At maturity the sporophyte splits into two valves, and the spores are gradually thrown out as they mature. Owing to the formation of new sporogenous tissue at the base of the sporophyte, spores in all stages of development occur in the same individual.
+
+![]()
+A C E
+B D
+
+
+Fig. 185. — *Antherocera Porensis*. Development of the embryo (x 300). A, C, E, median longitudinal sections. B, D, successive cross-sections of embryos of about the age of A, C, E, older embryo, showing the archegonium.
+Class III. Musci
+The true Mosses (Musci) are much more abundant than the Hepa-
+tics, especially in colder regions, where they often constitute an important feature of the vegetation. While the number of species is much greater than that of the Liverworts, the general type is a very uniform one, and were it not for the peculiar genera, Sphagnum and Andreae, they might all be reduced to a single order.
+
+The Gametophyte
+*Protonema*. — The gametophyte of the Musci always shows a preliminary stage, the protonema, which is usually an extensively branch-
+ing growth, resembling an Alga, or, less commonly, is a flat thallus
+
+324
+BOTANY
+
+![]()
+A. A longitudinal section of the base of the root.
+B. A circular section. Note the arrangement of the cells in the cortex.
+C. The epidermis of the root.
+D. A transverse section of the root.
+
+
+Fig. 106. Anthoceros Purpureus. A. transverse section of the base of the root. B. circular section. Note the arrangement of the cells in the cortex. C. epidermis of the root. D. transverse section of the root.
+
+14
+
+THE ARCHEGONIATE. 225
+
+like that of the simple Hepaticae. The protonema arises primarily from the germination of the spore, but may develop secondarily from various parts of the gametophyte, or even, in exceptional cases, from the sporophyte. From the protonema special branches arise, which become the leaf shoots, or gametophores, upon which the sexual organs are borne.
+
+The leaves of the filamentous protonema is apical, and the divi-
+sion walls are often strongly oblique, this being especially the case in the branches which penetrate the earth and assume the character of rhinoids. These branches lose the chlorophyll, and their cell-walls
+
+![]() A: A fragment of a protonemal filament, with young bud developing from it.
+B: The same bud in optical section.
+C: An older bud, from which a new filament has been formed (x 20).
+D: Protonemal filaments with an older bud, pure, attached (x 30).
+r: Gametophore.
+gam: Gametophore.
+
+become thick and brown in color. In Sphagnum the protonema is a flat thallus, which in its earlier stages often shows a two-sided apical cell, like that in the lower Hepaticae. From the margin of this thallus short branches grow out, forming a typical gametophore. It is probable that the thalloid protonema of Sphagnum is an older type than the filamentous type of the typical Mosses.
+
+Gametophores usually shoot begin to appear at the end of the
+protonema (Fig. 187). These shoots are very slender, and there are formed, in rapid succession, three intersecting walls, which cut out a tetrahedral apical cell, from which are then cut off three series of
+
+4
+
+236
+BOTANY
+
+segments, each of which gives rise to a leaf and a portion of the stem.
+From the base of the young shoot rhizoids grow out, which fasten it to the ground. These rhizoids may, under proper conditions, give rise to new protonemal filaments.
+
+Apart from the usual mode of growth exceptions (e.g. Fissidens), the growth of the shoot in the Musci is from the activity of a tetrahedral apical cell (Fig. 189), and the shoot is radially symmetrical. Each segment of the apical cell gives rise to a leaf and a portion of the
+
+![]() A. B. C. D.
+
+FIG. 189. — *Pterocha pedunculata.* *d.*, leafy shoot with gemmae (*× 6*). *B.*, upper part of the same (*× 30*). *C.*, young gemma (*× 600*). *D.*, older gemma (*× 500*).
+
+stem. The branching is always lateral, the apical cell of the branch being cut out from an outer cell of the stem, below one of the young leaves.
+
+The Leaf. — The growth of the young leaf is from a two-sided apical cell, whose growth is limited. The later growth is basal. In Sphagnum, Fontinalis, and a small number of other Mosses, the leaf develops no vascular system at all; but in most other Mosses there is a specialized strand, whose central cells are for purposes of conduction. The rest of the leaf is usually composed of a single layer of uniform green cells; but in Sphagnum there are two kinds of cells, large empty
+
+THE ARCHEGONIATE
+227
+
+![]() A median longitudinal section of a strong shoot; x, spiral cell; z, initial of a lateral branch (× 300). B, transverse section of the apex (× 300). C, similar section of a young branch (× 900).
+![]() A transverse section of the apex of a young shoot (× 515). B, C, cross-sections of young leaves (× 515). D, cross-section of stem (× 387).
+
+228
+BOTANY
+
+ones, surrounded by narrow green ones (Fig. 202). In Polytrichum the midrib is very largely developed, and there are special vascular plates of green tissue, placed amongst the leaves, thus increas-
+ing the amount of assimilating surface
+(Fig. 191, B).
+
+A.
+The primitive three-ranked arrangement of leaves is in most cases replaced by a greater number of rows, caused by early inequalities in the growth of the young parts.
+
+The shoot may have a limited growth, dying after the reproductive organs are formed; or it may grow for many years, giving rise to special branches upon which the reproductive organs are developed. Except in Sphagnum there is an axial strand of conducting tissue, and usually the outer tissues are composed of thick-walled cells, so that the stem is more or less woody in texture.
+
+In the peculiar genus Buxbaumia the gametophore shoot is rudimentary, and the leaves are reduced to scales. This is due to the saprophytic habit of the plant which lives upon decaying wood, into which the rhizoids penetrate, much as do the hyphae of a Fungus.
+
+Fig. 191.—A cross-section of leaf of Lecanogynum, similar section of leaf of Polytrichum, and a section of Sphagnum cellule. (After Gourlay.)
+
+Reproduction
+
+Gemmae.—In many Mosses the forma-
+tion of sexual reproductive organs is exceedingly rare, and the plants increase non-sexually by the separation of branches. In some Mosses special gemmae, not unlike those of the Hepaticae, are developed, but these are not found in all species of the same genera (Fig. 188). Resting-buds are common, however, upon the proto-
+nema. These appear to be, as a rule, arrested gametophore buds.
+
+Sex-organ.—The antheridium, in all investigated Mosses, grows at first from a two-sided apical cell (Fig. 192). A long stalk is developed in Sphagnum,
+but in most other genera it is short. The antheridium is generally club-shaped, and the peripheral cells contain numerous chromatophores, which often show a red or orange color when ripe. In Sphagnum the large, nearly globular antheridia are produced by several tubules which break out on the sporocelis free. In Bryopsis the upper cells separate, and after the whole
+
+THE ARCHEGONIATE 229
+
+mass of sperm-cells has been discharged, the opening closes, so that the archi-
+thom looks very much as it did before it opened. The spermatoida are called
+filaments, with two extremely long cilia (Fig. 193, C).
+The early development of the archegonium (Fig. 194) in the Musci is much
+like that in the ferns. The neck canal-cell is first evident. The original
+cell of the neck, which in the Hepaticae divides by intersecting walls to form
+the cover-cells, is here represented by the cell A. The archegonium
+whose further growth is due to its division. It has the form of a truncated,
+three-angled pyramid. Segments are cut off from the three lateral faces, and
+from the inner, truncate portion. The latter segments contribute to the
+
+![]()
+A. B. C. D.
+
+
+![]()
+E. F. G. H.
+
+
+Fig. 195.—Fern-like Archeogonia. Development of the archithom. A, Z., longitudi-
+nal sections (× 600). D, section in a plane at right angles to C. E, optical
+section (× 800). F, G, cross-sections. H, diagram of cross-section, showing the
+early divisions.
+1, young spermatoida (× 200).
+neck canal-cell, the lateral segments, which undergo a longitudinal division,
+add to the archithom. In addition to these cells and its sister cell, the
+ventral canal-cell, are formed as in all the Archegoniate.
+
+**Fertilization.** —Fertilization is effected when the sexually mature
+plants are covered with water. The substance which attracts the
+spermatoida to the open archegonium has been shown to be cane-
+sugar.
+
+The reproductive organs are sometimes surrounded by somewhat
+modified leaves, which gives the end of the shoot the appearance
+
+230
+BOTANY
+
+![]() A diagram showing various stages of a plant's life cycle.
+
+C.
+E.
+
+A.
+D.
+
+B.
+
+Fig. 103. — *Funaria hygrostemon*. A, ripe antheridium which has just discharged the spermo-cells, $E_1$ ($\times 300$). C, spermatoids ($\times 1300$). D, paraphysis ($\times 300$).
+$E_2$, male - flower of *Atrichum undulatum* ($\times 6$).
+
+---
+
+THE ARCHEGONIATE231
+
+of a flower. This is especially noticeable in the antheridial receptacles of some Mosses, like Polytrichum and Funaria. In Sphagnum the antheridia are borne singly in the axis or close imbedded leaves which are often very long, so that the antheridial catkin-like shoots are very noticeable.
+
+The Sperophytes. --- The sperophyte in the higher Mosses becomes highly specialised, but in all but Sphagnum the development in the earlier stages is similar.
+
+Sphagnum. --- The embryo of Sphagnum resembles very much that of the Anthocerotales, and suggests an affinity with that group. The young embryo (Fig. 308) shows the formation of several tiers of cells, and an early differentiation.
+
+![]()
+A. A.
+B. B.
+C. C.
+D. D.
+E. E.
+F. F.
+G. G.
+
+
+Fig. 308. --- Funaria Aggregatiorum. Development of the archegonium. B, optical section; F, surface view; the others longitudinal sections. G, paraphyses.
+( \(\times\) 150.) (After Hennig.)
+x x x
+
+tion of endosteleum and amphisteleum. As in the Anthocerotales, the archesporium is derived from the amphithectum, in which respect Sphagnum differs from all the other Musci. The archesporium extends over the top of the columnella to form a cup-like structure.
+
+The basal growth of the young sperophyte is limited, and at maturity it is a globular or oval capsule, with a large foot imbedded in the end of the gametangium which is usually surrounded by a thickened wall, and closed by a circular lid.
+
+By means of which typical Mosses (Bryales) the embryos (Figs. 168, 169) first divide by a transverse wall into two nearly equal cells. In the upper (epibasal) half, the next walls are inclined and a large two-sided apical cell is formed, which continues to divide for a long time, and causes a rapid increase in length of the embryo, which becomes spinule-shaped. Later the apical growth
+
+232
+BOTANY
+
+![]() A diagram showing the development of the embryo. A. Optical section of very young embryo. B. 1, 2, surface view and optical section of an older one (× 600). C, D, median sections of older embryos (× 600); en, endosperm; am, amphilectum.
+
+Fig. 15. - Puccinia hypotricha. Development of the embryo. A, optical section of very young embryo; B, 1, 2, surface view and optical section of an older one (× 600); C, D, median sections of older embryos (× 600); en, endosperm; am, amphilectum.
+
+THE ARCHEGONIAT.E 235
+
+cesses, and the subsequent growth of the sporophyte is basal, much as in Anthocerotae.
+
+An early division of the tissues into endodermis and amphithecium is apparent, but the archesporium is derived from the cells below the endodermis, and not from the amphithecium as in Sphagnum.
+The archesporium is restricted to a relatively small part of the sporophyte. In the aberrant genus Archidium no definite archesporium is developed, but otherwise the sporophyte conforms to the usual type.
+
+As the sporophyte develops, the upper part enlarges and forms the capsule (Fig. 197). This enlargement is in part due to increase in the number of cells, partly to the development of a large air-space between them. This space arises
+
+![]() A B C D E
+Fig. 196. -- *Pteridium Arpogenum.* Five transverse sections of a young embryo.
+A, just before division; B, the others show stages down to A. 4000.
+
+in the amphithecium, and is separated from the archesporium by two or three layers of cells. Some of the cells remain in contact, and elongate so as to occupy the space enlarged, and form lamella-like filaments extending across it. These cells, as well as those which have been formed by division, constitute a mass of parenchyma. The formation of the capsule does not develop any apoprogenous tissue, but forms a mass of green parenchyma, often with conspicuous air-spaces, and constituting the principal part of the sporophyte. The epidermis is thin and delicate; this "Apophysis" has perfect stomata (Fig. 198) developed in the epidermis.
+
+The lower part of the sporophyte forms a slender stalk or axis, which terminates below in a bulbous base. The axis soon divides into a definite central strand of conducting tissue, suggesting the vascular bundles of higher plants.
+
+The archesporium forms a cylindrical layer about the central columnella of the capsule, but does not extend over it. The upper portion of the capsule becomes the lid or "Operculum," which is found in some but not all Bryopsids. Where the operculum joins the Tectus, or open-molding part of the capsule, the latter
+
+354
+BOTANY
+
+has the cells forming its margin much thickened. Above these is a ring of large, thin-walled cells, the Annulus, which finally are destroyed, and effects the separation of the operculum from the theca.
+
+![]() A diagram showing the structure of a bryozoan theca.
+
+A.
+B.
+C.
+D.
+E.
+F.
+G.
+H.
+I.
+J.
+K.
+L.
+M.
+N.
+O.
+P.
+Q.
+R.
+S.
+
+Fig. 197. — Funicular approximation. A, longitudinal section of a nearly ripe capsule (× 300); p., peristome; r., annulus; t., thickened cells forming the rim of the theca. B, sporogenous cell, shortly before the final division (× 400); t., inner, outer, and middle layers of the wall; s., spore; o., apophysis (× 400); e., exine; a., mala; o., apophysis; a.p., apores; o.t., columella; r., annulus; s., operculum.
+
+Beneath the operculum there are developed, in most Bryales, the peculiar structures forming the "Peristome." The peristome is usually composed of the remains of the thickened cell-walls of special cells, which are separated from the wall of the operculum by two or three layers of thin-walled cells. These are called "Epipyle" or "Epipyle ripens." The peristome usually has the form of teeth fringing the margin of the theca. These generally are in two rows, representing
+
+THE ARCHEGONIATE
+235
+
+![]()
+A. Young, B. older, stoma, from the base of the capsule.
+C. Section of a stoma (× 360).
+
+
+Fig. 198. — *Funaria hygrometrica*. A, young, B, older, stoma, from the base of the capsule. C, section of a stoma (× 360).
+
+the inner and outer walls of rows of cells extending from the edge of the theca, under the operculum. The peristome is highly hygroscopic, and as the water evaporates on the sporophyte approaching maturity, the outward pressure of the peristome helps to throw off
+
+![]()
+A. Barbelia foliis, upper part of exostome, showing the slender, twisted teeth of the peristome.
+B. *Pseudoceros* foliis, upper part, showing double peristome. (After Scou.) C. *Polytrichum commune*, peristome and epiphyllagma (× 8). D, *P. commune*, ripe capsule; 1, with 2, without, the calyptra (× 3).
+
+
+Fig. 199. — A. Barbelia foliis, upper part of exostome, showing the slender, twisted teeth of the peristome. B. *Pseudoceros* foliis, upper part, showing double peristome. (After Scou.) C. *Polytrichum commune*, peristome and epiphyllagma (× 8). D, *P. commune*, ripe capsule; 1, with 2, without, the calyptra (× 3).
+
+236
+BOTANY
+
+the operculum, loosened by the destruction of the cells of the annu-
+hua. After the operculum is thrown off, the peristome, with its hygroscopic elements, assists in removing the spores from the theca. The seta also is often hygroscopic. All of the archesporial cells develop spores. The latter are usually small and contain chlorophyll.
+
+The vexillum of the archegonium becomes very large in most Mosses,
+
+![]() A diagram showing a moss plant with various parts labeled.
+
+Fig. 300. — *Sphagnum* sp. A, B, young protonemata (× 200). C, older protonema with leafy bud, &c (× 30); r, marginal rhizoids.
+
+and forms a bell-shaped calyptra about the slender embryo. Finally it becomes torn away, and is carried up by the elongating sporophyte, whose summit is protected for a long time by this conspicuous membranaceous cap.
+
+**Classification of the Musci**
+
+The Musci may be divided into three orders,—Sphagnales, An-
+dreaceae, and Bryales,—of which the latter comprises an over-
+whelming majority of existing Mosses.
+
+THE ARCHEGONIATE
+287
+
+Order I. Sphagnales
+
+The Sphagnales are represented by the single genus Sphagnum.
+They are aquatic or semiaquatic Mosses of simpler structure than
+
+![]()
+A: A Sphagnum gametophyte. A. C. Curtis from a young leaf (× 600).
+B: A leaf from an older leaf.
+C: A leaf of the same plant showing the sporangia (× 600).
+D: A leaf of the same plant showing the thallus protonema and the peculiar embryo (× 600).
+E: The thallus protonema and the peculiar embryo.
+F: A section through a leaf of Sphagnum.
+G: A section through a leaf of Sphagnum.
+H: A section through a leaf of Sphagnum.
+I: A section through a leaf of Sphagnum.
+J: A section through a leaf of Sphagnum.
+K: A section through a leaf of Sphagnum.
+L: A section through a leaf of Sphagnum.
+M: A section through a leaf of Sphagnum.
+N: A section through a leaf of Sphagnum.
+O: A section through a leaf of Sphagnum.
+P: A section through a leaf of Sphagnum.
+Q: A section through a leaf of Sphagnum.
+R: A section through a leaf of Sphagnum.
+S: A section through a leaf of Sphagnum.
+T: A section through a leaf of Sphagnum.
+U: A section through a leaf of Sphagnum.
+V: A section through a leaf of Sphagnum.
+W: A section through a leaf of Sphagnum.
+X: A section through a leaf of Sphagnum.
+Y: A section through a leaf of Sphagnum.
+Z: A section through a leaf of Sphagnum.
+AA: A section through a leaf of Sphagnum.
+BB: A section through a leaf of Sphagnum.
+CC: A section through a leaf of Sphagnum.
+DD: A section through a leaf of Sphagnum.
+EE: A section through a leaf of Sphagnum.
+FF: A section through a leaf of Sphagnum.
+GG: A section through a leaf of Sphagnum.
+HH: A section through a leaf of Sphagnum.
+II: A section through a leaf of Sphagnum.
+JJ: A section through a leaf of Sphagnum.
+KK: A section through a leaf of Sphagnum.
+LL: A section through a leaf of Sphagnum.
+MM: A section through a leaf of Sphagnum.
+NN: A section through a leaf of Sphagnum.
+OO: A section through a leaf of Sphagnum.
+PP: A section through a leaf of Sphagnum.
+QQ: A section through a leaf of Sphagnum.
+RR: A section through a leaf of Sphagnum.
+SS: A section through a leaf of Sphagnum.
+TT: A section through a leaf of Sphagnum.
+UU: A section through a leaf of Sphagnum.
+VV: A section through a leaf of Sphagnum.
+WW: A section through a leaf of Sphagnum.
+XX: A section through a leaf of Sphagnum.
+YY: A section through a leaf of Sphagnum.
+ZZ: A section through a leaf of Sphagnum.
+
+the Bryales, and, as already indicated, showing certain affinities with the Anthocerotales. The thallous protonema and the peculiar embryo have been referred to.
+
+Fig. 301.—Sphagnum gemmatum.
+
+238
+BOTANY
+
+The shoot grows much as in the Bryales, but no midrib is develop in the leaves and no central strand in the stem. The leaves are characterized by the peculiar empty cells between the narrow green cells, and these empty cells usually are marked with thickened bars, and have round holes in them, so that the cells take up water.
+
+![]() A, B, C, D, E, F, × 300; C, × 315; D, × 150.
+
+Fig. 203. — *Sphagnum crenatifolium.* Development of the embryo. (After WALDEN.)
+
+(A, B, E, F, × 300; C, × 315; D, × 150.)
+
+very quickly. Similar empty cells form the cortex of the stem, and also soak up great quantities of water, so that the masses of growing plants take up water like a sponge. The empty cells give them a pseudo-epidermis.
+
+The sporophyte develops no seta, but the end of the shoot to which it is attached often grows out beyond the leaves, forming a "pseudo-
+
+THE ARCHEGONIATE. 239
+
+podium," which gives the capsule the appearance of having a seta (Fig. 20).
+
+The species of Sphagnum are especially abundant in moist northern countries, where they form the most important element in the peat-bogs. The plants are perennial, forming new shoots at the top and slowly dying away below, the compact masses of dead tissue becoming gradually transformed into peat.
+
+Order II. Andrenales
+
+This order has but a single genus, Andrena, a plant with a single sporophyte (Fig. 20). It grows upon rocks, and to some degree intermediate between the Sphagnales and Bryales, but the whole approaching more nearly the latter order (Fig. 204). The peridome is more or less persistent, and the archesporium, although derived from the endodermis, extends over the top of the sporophyte. The capsule opens by four longitudinal slits.
+
+Order III. Bryales
+
+All of the commoner Mosses except Sphagnum belong to this order. They show great diversity of size and have adapted themselves to a great variety of environment. A few, like Fontinalis and Amblystegium, are true aquatics. Most of them prefer moist, shaded situations upon the earth or upon trunks of trees; some however, thrive in exposed situations where they grow in clusters or at least in tufts.
+
+Classification. — The Bryales are sometimes divided into two orders, Cleitostocarpe and Stegocarpe, based upon the method of dehiscence of the capsule. The former, e.g. Plutonium, Ephemerum, do not dehisc by opening up their own bristles (Fig. 205). There is no question, however, that the two groups are closely related.
+
+Another division, based upon the position of the sporophyte, is
+
+![]() A diagram showing a plant with a single sporophyte (B) and a mature sporophyte (A).
+Fig. 206.—Andrena petrophila. A, plant with mature sporophyte (× 10); B, longitudinal section of sporophyte (× 80); pa., pseudo-podium; col., collet.
+Pa
+
+340
+BOTANY
+
+sometimes made. Where it is terminal, i.e. borne upon the main shoot, as in Polytrichum or Funaria, it is said to be "acrocarpous"; where the fertile shoots are lateral ones, the plant is said to be "pleurocarpous," as the genus Hypnum.
+
+The division into genera is largely made upon the character of the peristome, and especially the peristomial cells. The latter is wanting in a few of the genera, such as Gymnopus and Sphagnum; but in all those the peristome arises from the splitting of the whole mass of tissue beneath the operculum into four teeth. In the Polytrichaceae (Fig. 196 C) the peristome is composed mainly of peculiar thallus-cells, and the mouth of the thallus covered by a "epithelium" com-
+posed of a single layer of cells. In much the greater number of the peristome is composed merely of the remains of the cell-walls of the peristomial cells.
+
+BIBLIOGRAPHY
+
+95. I. Barnes, C. R., and Head, F. D. Analytic Keys to the Genera and Species of North American Mosses. Madison, Wis., 1890.
+96. Capps, W. H., and Fernald, M. L. Manual of North American Bryophytes and Fungi. London and New York, 1895. (Contains full bibliography of the subject.)
+97. ————. The Development of Geothallus tuberous. Ann. of Bot., X. 1896.
+98-'01. Ruger and Frantz. Max. Phanerogam. Thall 1. Abt. 3. Hepatium.
+Schimper, Y., and Muell.-Argyi, C., and Boulard, W. 1896-1901.
+(Contains full bibliography.)
+97'. Gobius, J., and Schimper, Y. Die Systematische Botanik der Pflanzen und Tiere. Berlin, 1870.
+900. -———-. Organography of Plants. Oxford, 1900.
+990. Howe, M. A. The Hepaticae and Anthocerotae of California. Mem.
+of Calif. Acad. Sci., 1887.
+98'. Leaquerzur, L., and James, T. P. Manual of the Mosses of North America. Boston, 1884.
+97'. Leopold, Chr.. Handbuch der Systematischen Botanik, I. Leipzig, 1879.
+97'. Müller, H., and Frantz, W.
+71'. Ruhland, W., See Engler and Prantl.
+72'. Schiffter, V., See Engler and Prantl.
+98'. Umney, L., M., The Hepaticae. Gray's Manual of Botany, 6th ed.
+1890.
+96'. Vines, S. H., Text-book of Botany. London and New York, 1896.
+96'. Whiting, E., Jr., Handbook of Systematic Botany. London and New York, 1886.
+
+PLATE III
+
+Tree-ferns growing in a Brazilian forest. (Photograph by Dr. J. C. Branner.)
+
+UOFM
+
+Mmol
+
+CHAPTER VIII
+
+PTERIDOPHYTTA (Ferns)
+
+In most Bryophytes the gametophyte is the predominant phase, and the sporophyte is relatively unimportant; in Anthoceros and some Mosses, however, the sporophyte is large and develops a complex system of assimilating tissue, so that it becomes almost independent of the gametophyte. Ferns, however, do not sporophytes develop roots. In the Pteridophytes, or Ferns, and their allies, the sporophyte early develops a root which puts it into communication with the earth, and it thus becomes more independant of the gametophyte.
+
+With the increasing importance of the sporophyte, which is also larger and often of large size, there is a reduction of the gametophyte, which may become reduced to a few cells, completing its whole development within twenty-four hours.
+
+In most Pteridophytes the gametophyte (called the "Prothalium") is a small plant with reduced leaves and simpler thalloe Liverworts. In exceptional cases it may reach a length of several centimeters in a few months, or even years (Fig. 205). In certain forms, e.g. Botrychium, *Lycopodium clavatum*, it is a subterranean tuberous body, quite destitute of chlorophyll, and living as a saprophyte.
+
+ budding Gametophyte. — Where the gametophyte is large and long-lived, it is not infrequently multiplies by the formation of special
+
+![]() A diagram showing a fern-like plant with a large sporophyte at the top and a smaller gametophyte at the bottom.
+![]() B A diagram showing a fern-like plant with a large sporophyte at the top and a smaller gametophyte at the bottom.
+![]() C A diagram showing a fern-like plant with a large sporophyte at the top and a smaller gametophyte at the bottom.
+
+Fig. 268. A. *B. Muscari tenuifolium*. Gametophyte, the apex divided dichoto-
+mously, and with lateral buds, $k$ ($\times$ 2). B. *Anthoceros furfuraceus*. Sporophyte,
+attached. C. *Anthoceros furfuraceus*. Gametophyte with four sporophytes attached.
+ep. (Natural size.)
+
+*341*
+
+243
+BOTANY
+
+buds, or gemmae, which may be produced in large numbers. It also bears monosacrally or dichotomously the sexual organs of the
+Arthogonium. The sexual organs of the Pteridophytes are similar to those of the Bryophytes. The Archegonium (Fig. 206) has the venter imbedded in the tissue of the gametophyte, and the neck has but four rows of peripheral cells. The four rows of neck-cells probably represent the four segments of the archesporial cell of the archegonium of the Liverworts. Of the Bryophytes, the Anthocerales come nearest the lower Pteridophytes in the character of the sexual organs. Except in Lysopticum, where the number of canal-cells is large, the neck shows but two canal-cells in the Pteridophytes.
+
+![]() A: Asexual reproduction diagram showing a leaf with a bud emerging from its base.
+![]() B: Diagram showing asexual reproduction in a fern, with a new frond emerging from a leaf.
+![]() C: Diagram showing asexual reproduction in a moss, with a new plant emerging from a leaf.
+
+Fig. 201.--Struthiopteris gracilis.
+Fig. 207.--Osmunda Cinctorum.
+A, ripe antheridium; B, the same discharging the spermatozoa; C, spermatangia.
+
+The phytomastax is always present, and as in the Bryophytes is the sister-cell of the egg-archegonium. The antheridium (Fig. 207) in the lower types, such as Lycopodium and Marattia, is buried in the prothallial tissue as it is in Anthoceros. In the more specialized Ferns it projects and forms a single spherical body, within which is a single layer of chlorophyll-bearing cells, within which is a mass of colourless sperm-cells. In the Club-mosses, the small spermatangia are biciliate like those of the Bryophytes; in the Ferns and Horsetails they are larger, and have many cells.
+
+This development of the spermatangia (Fig. 208) has been followed in several Ferns and in Equisetum. In the later divisions
+
+PTERIDOPHYTA
+348
+
+of the sperm-cells, a peculiar body, the blepharoplast, becomes visible.
+This closely resembles the centrosomes found in some plants, and is sometimes considered to be of the same nature. After the final divi-
+sions each cell contains a single nucleus, and a blepharoplast lying close to the nucleus, in which no nucleolus can be seen.
+
+The nucleus becomes elongated, and assumes a crescent form,
+gradually becoming longer and assuming the coiled form of the per-
+fect spermatoid, most of which is derived from the nucleus of the
+open-celled sporangium. The blepharoplast also becomes elongated
+to the nucleus, beyond which it projects as the anterior cilia-bearing
+end of the spermatoid. The cilia are, apparently, developed exclusively from the blepharoplast.
+
+![]()
+A - A
+B - B
+C - C
+D - D
+E - E
+F - F
+b - b
+n - n
+n - n
+
+
+Fig. 358. — *Mauritia flexuosa*. Development of the spermatocyst (x 1000); A, blepha-
+roplast; A-C, last division, preliminary to the formation of the spermatoid.
+D-F, development of the spermatoid; n, nucleus of spermatoid.
+
+**Fertilization.** — As in all other Archegoniates, the opening of the reproductive organs is dependent upon the access of water, and is accomplished by means of a hygroscopic bladder. In contrast with
+from the open archegonium of various Ferns, it has been shown that malic acid is present, which exercises a strong attraction upon the spermatocysts. On reaching the open archegonium, the spermato-
+cysts creep into its cavity, often by means of their cilia, and fill-
+ing the neck retard their movements somewhat, and detaches the
+vesicle attached to the hinder coil of the active spermatoid.
+The spermatoid moves slowly by a spiral motion through the narrow
+neck-canal; until it reaches the central cavity in which is contained
+the egg. The first spermatoid to enter penetrated at once into the
+egg.
+
+The fusion of the spermatoid with the egg-nucleus (Fig. 215)
+is slow in the common Ferns, where it has been most completely
+
+244
+BOTANY
+
+studied. The spermatocid retains its original form for some time, and is recognisable even after it has penetrated into the cavity of the egg-nucleus. Here it slowly changes form, approaching the condition of the original sperm-nucleus. The chromosomes become more evident, and finally are not distinguishable from those of the egg-nucleus.
+
+The egg-cell has, in the meantime, been slowly growing, and is provided with an evident cell-membrane. The first division may occur after an hour or so, as in species of Marsilia; but in the common Ferns it is probably at least a week in most cases, and in other Ferns still longer.
+
+The Embryo
+
+The embryo in its earlier stages (Fig. 209) closely resembles that of the Bryophytes, and in the lower types of Pteridophytes the development of the special organs, leaf, stem, and root, may not occur until the embryo has reached a relatively large size. Sooner later, however, by the elongation of a leaf-organ and root, the young sporophyte becomes independent.
+
+When the young sporophyte is established, the gametophyte dies, and never again appears as an independent leafy plant, which in most cases lives many years.
+
+Sooner or later the sporophytic character of the plant is shown by the production of spores, which resemble in all respects those of the Bryophytes. They are borne in special organs, sporangia, which are of very characteristic structure in the different types of Pteridophyta. In some species, such as Ophioglossum, they are cavities in the leaf tissue filled with a great number of spores. Usually (Fig. 210) they are capacious, often stalked, borne upon special leaves, sporophylls, which are sometimes quite different from the foliage leaves, and arranged in a spike or cone, suggesting the flowers of the simplest Seed-plants.
+
+Spore-division
+
+The sporogenous tissue may sometimes be traced back to a single archesporial cell, but this is not always the case. The sporogenous
+
+![]() A diagram showing the early stages of embryonic development in Onoclea sensibilis and Riccia fluitans.
+Fig. 209. - A. Onoclea sensibilis. B. Riccia fluitans.
+Embryos showing the similarity in the embryo of these Ferns and Liverworts in early stages
+(× 300).
+
+245
+
+PTERIDOPHYTA
+
+245
+
+cells divide into four spores, precisely as in the Bryophytes, and the ripe spores have the same structure (Fig. 221).
+
+The nearest approach among Bryo-
+phytes to the segregation of the
+sporogenous tissue found in the
+Pteridophyta is that of the Antho-
+ceratales, where the groups of sporo-
+genous cells are separated by layers
+of sterile tissue somewhat as in
+Ophioglossum.
+
+Apogamy and Apsepy. — In
+several forms the sporophyte has
+been observed in certain instances
+to arise directly from the gametophyte
+instead of from the egg-cell. This non-sexual ori-
+gin of the sporophyte is known as
+Apogamy.
+
+A psepy is the development of
+the gametophyte as a bud of the
+sporophyte. These abnormal pro-
+ductions have been observed to develop
+from the margin or from the surface
+of a leaf, or in some cases from the
+transformation of a young sporan-
+gium into a leaf.
+
+Distribution of Pteridophytes. — The sporophyte in most Pterido-
+phytes is terrestrial, but a few
+forms are aquatic. Salvinia and Azolla
+lacustris is completely submerged, while Salvinia and Azolla are
+floating forms. Marsilia is usually amphibious. The Pteridophytes,
+like the Hepaticae, reach their greatest development in the moist
+mountain forests of the Tropics, where they constitute an important
+and much sought-for form of vegetation. The ferns which live like the little Gold-back Fern (Gymnosporangium triquetrum), are adapted to a dry region, and can endure complete desiccation with-
+out injury.
+
+The living Pteridophytes are usually divided into three classes,
+Filicales, Equisetales, and Lycopodales. Of these the first com-
+prises much the greater number of existing species. The Equisetea,
+which during the Paleozoic age were numerous and varied,
+now comprise but a single genus. Lycopodales were abundant
+during this period but no plants developed later than they are at present. There
+
+![]() A - Spore
+![]() B - Spore
+![]() C - Spore
+![]() D - Spore
+![]() E - Spore
+![]() F - Spore
+![]() G - Spore
+![]() H - Spore
+![]() I - Spore
+![]() J - Spore
+![]() K - Spore
+![]() L - Spore
+![]() M - Spore
+![]() N - Spore
+![]() O - Spore
+![]() P - Spore
+![]() Q - Spore
+![]() R - Spore
+![]() S - Spore
+![]() T - Spore
+![]() U - Spore
+![]() V - Spore
+![]() W - Spore
+![]() X - Spore
+![]() Y - Spore
+![]() Z - Spore
+
+**Fig. 220. — Lycopodium, elementum.**
+
+A, leaf-shoot having two cones on opposite sides (dorsal); B, single sporophyll, with sporangium, ep., enlarged; C, cross-
+section of sporophyll showing sporangia; D, section through sporangium showing spores; E, section through sporangium showing spores; F, section through sporangium showing spores; G, section through sporangium showing spores; H, section through sporangium showing spores; I, section through sporangium showing spores; J, section through sporangium showing spores; K, section through sporangium showing spores; L, section through sporangium showing spores; M, section through sporangium showing spores; N, section through sporangium showing spores; O, section through sporangium showing spores; P, section through sporangium showing spores; Q, section through sporangium showing spores; R, section through sporangium showing spores; S, section through sporangium showing spores; T, section through sporangium showing spores; U, section through sporangium showing spores; V, section through sporangium showing spores; W, section through sporangium showing spores; X, section through sporangium showing spores; Y, section through sporangium showing spores; Z, section through sporangium showing spores.
+
+246
+BOTANY
+
+are also a number of fossil types of Pteridophytes which are not assignable to any of the three existing classes.
+
+CLASS I. FILICALES
+The Filicales, or Ferns, are cosmopolitan, but much more abundant in the moist Tropics than elsewhere. In northern regions a few species like *Pteridium aquilinum* or *Osmunda regalis* may be abundant enough to attract notice, but most of the northern Ferns are compar-
+
+![]() A B C D E
+
+Fig. 311. - Spore-division in *Equisetum*. A, D, E, K. *telematia* (× 400). B, C, *E. limosum*, most highly magnified. A, group of four spongyous cells; fig. C, five nuclei in a vesicle; fig. D, walling off of the first division.
+E, division of the cell into the young spores. (B, C, after Ostenhous.)
+
+Atively insignificant. In the Tropics, however, especially in the mountains, they often occur in great numbers and variety, and some of the Tree-ferns are among the most striking of all plants.
+
+(The Gametophyte)
+
+The gametophyte (Fig. 312) of the Ferns is a flat, green thallus, which in exceptional cases (*e.g.* *Vittaria pinnata*) may reach several centimetres in length and branch repeatedly.
+
+The ripe spore usually shows three membranes, the inner cellulose
+
+PTERIDOPHYTA
+247
+
+membrane (Intine), the cuticularized exine or "Exospore," and the outermost sculptured coat or perinium ("Epiarep") which some-
+![]()
+A. A young gametophyte.
+B. A young gametophyte with apical cell.
+C. An older stage with apical cell.
+D. A young sporophyte.
+E. A mature sporophyte.
+F. Small sporophyte, seen from below; r, rhizoids; ar, archegonia.
+
+
+Fig. 212.--Struthiopteris Germanica. A, B, germinating spores, with perinium removed (x 300). C, young gametophyte (x 100). D, E, older stages with apical cell; x 5 (x 300). F, small sporophyte, seen from below; r, rhizoids; ar, archegonia.
+
+times becomes detached from the exopore. In case the spore con-
+tains chlorophyll at maturity the germination is usually rapid; in
+
+248
+BOTANY
+
+Osmunda the first division of the spores may take place within less than twenty-four hours. Where chlorophyll is not present the process of germination is retarded, as chlorophyll must be developed before any further growth takes place.
+
+Germination. In ferns, Fersn the first division in the germinating spore (Fig. 102) occurs in the apical cell, which forms the first root-hair, from a larger green cell which gives rise to a row of cells varying in length under different conditions. In the terminal cell of the row a two-sided apical cell is formed by interecting with the outer side of the first root-hair, and this is the thallus. New root-hairs grow out from the lower side, and fasten it to the earth. At this stage the young gametophyte closely resembles a simple thallus Liverwort, such as Metzgeria or Aneura, and is thus called a simple gametophyte. The upper part of the heart-shaped thallus, caused by the rapid growth in the outer cells of the young segments cut off from the main cell.
+
+Sooner or later the two-sided apical cell is divided by a transverse wall and two lateral cells are produced. These segments are regularly cut off, which undergo horizontal divisions, so that back of the apex the thallus forms a cushion of tissue, upon whose lower surface the archegonia are later developed. If this thickening begins early, as in Osmunda, then only a small thallus is developed. The root-hairs develop little or no chlorophyll, but they contain numerous discoid chlorenchymes.
+
+Both archegonia and antheridia are borne upon the same plant in most Ferns (e.g., Asplenium), but in some tropical Ferns, especially species of Vittaria and Hymenophyllum, in which the gametophyte may reach a length of several centimeters and fork repeatedly, like a thallous Liverwort, which it closely resembles. These plants reproduce themselves rapidly by the development of gemmae, and thus they may occur in great numbers, forming thick mats upon the trunks of trees, or upon rocks.
+
+The Sexual Organs
+
+Anthoceridium. --This anthoceridium in the lower Ferns shows a slight analogy with that of the Anthoerolesales, especially those forms in which a single anthoceridium produces many spores. In the Anthoerolesales, the cell from which the anthoceridium develops arises by a transverse division of a superficial cell into an outer and an inner cell. The latter, which in the Anthoerolesales gives rise to the
+
+PTERIDOPHYTA
+249
+
+whole antheridium, in the lower or eusporangiate Ferns, develops at once into the mass of sperm-cells, while the outer wall remains as the covering of the egg. The question arises whether this type of antheridium may have been derived from that of the Anthocero-
+tales by a suppression of the sterile cells of the endogenous anther-
+idium, whose peripheral cells are replaced by the superficial cells
+covering the cavity in which the antheridium is situated.
+
+![]()
+A. A. E.
+B. B. C.
+C. C. D.
+D. D.
+
+
+Fig. 23. -- *Struthiopteris germanica*. Development of antheridium. A-C. vertical sections (× 600). D. nearly ripe sperm-cells. E. spermatoid (× 200).
+
+In the more specialised Ferns (Leptosporangiate), especially the
+Polypodiaceae, the antheridium (Fig. 213) projects as a nearly spherical
+body, in which the cell-divisions are very regular. In the Polypo-
+diaceae the hemispherical mother-cell is first divided by a funnel-
+shaped partition into two parts, one of which is in contact with the
+basal wall of the antheridium. The next wall is dome-shaped, and its base is in contact with the first-formed wall.
+
+250
+BOTANT
+
+Finally a concave wall is formed above the dome-shaped one and meeting it. The young antheridium now consists of a central cell enclosed by three peripheral cells, the two lower being ring-shaped, the upper one somewhat lenticular. These outer cells contain chro-
+matophores which are absent from the central cell.
+
+In the lower Lecanora, Struthiopteris germanica, Hymenophyllum — there are more than three peripheral cells, and there may be a special opercular cell, as there is in the Marattiae.
+
+The first division of the central cell is usually vertical, and this is followed by several other divisions, so that there are usually thirty-
+two to sixty-four sperm-cells finally developed, although the number
+
+![]() A longitudinal section of apex of prothallium: apical cell, x (× 215). B-D, archegonia (× 630). A shows the position of the archegonium in relation to the prothallium.
+
+Fig. 214. — *Struthiopteris germanica*. Development of archegonium. A, longitudinal section of apex of prothallium: apical cell, x (× 215). B-D, archegonia (× 630). A shows the position of the archegonium in relation to the prothallium.
+
+is not always the same. Previous to the last division but two, the blepharoplast, from which the cilia are developed, make their appearance.
+
+The discession of the antheridium is caused either by the rupture of the concave wall, or else when a small apical cell is thrown off. The great distention of the peripheral cells then forces out the spermatoid sperm-
+cells, whose membrane soon completely dissolves and sets free the spermatoid. In the typical Ferns the spermatoids are relatively large and conspicuous in appearance, during the period before they are freed from which the numerous cilia extend. The larger posterior coils are mainly composed of the nucleus of the sperm-cell, and enclose a deli-
+cate vesicle containing the remains of the cytoplasm of the sperm-
+
+PTERIDOPHYTA
+261
+
+cell. This may become much distended, and often contains small granules of starch.
+
+Arachnogamia. In the typical Ferns the archegonium (Fig. 214) is formed upon the lower surface of the thickened cushion back of the apex. In Botrychium it is borne upon the upper surface of the subterranean gametophyte, and in Osmunda the archegonium forms two rows of cells, one on each side of the midrib. The egg-cell divides into two by a transverse wall, and the inner cell usually divides again into an inner or basal cell, and a central cell from which the egg-cell and canal-cells are formed. The outer cell, which corresponds to the epidermis, covers the egg-cell with its walls and divides by cross-walls into four cells, which, by a series of transverse divisions, give rise to the four-rowed neck characteristic of the
+
+![]()
+A diagram showing the structure of an archegonium.
+
+
+Fig. 215. — A. Osmunda cinerascens. Section of recently fertilized archegonium (× 400). A spermatium has penetrated the nucleus of the egg, and several are in the space between the egg-cell and the canal-wall. B. Osmunda cinerascens. Section of mature archegonium (× 300). (B, after SAWYER.)
+Pteridophytes. In the Polypodiaceae the two posterior rows remain shorter than the anterior ones, and the neck is curved backward, probably an adaptation for facilitating the penetration of spermatia towards a fertile leaf. In Lycopodium and all the Euphorbiaceae, the neck is straight. The base of the archegonium is always coherent with the surrounding tissue, as in the Anthocerotales.
+
+The middle cell of the original three is pointed above, and the portion of it can be seen in the canal-cell, which subsequently divides more or less completely into two. A second transverse, or concave division-wall, cuts off the ventral canal-cell from the egg, which later contracts so as not to fill the cavity of the venter. The walls of both these cells are hyphomyceteous at their origin, and effect the opening of the ripe archegonium when water is
+
+262
+
+216
+BOTANY
+
+applied. As already stated, the attractive substance thrown out has been shown to be malic acid.
+
+The Embryo
+
+In the common Fenns the first division of the embryo does not occur for a week or more after fertilization. The globular embryo (Fig. 216) then divides by a nearly vertical basal wall into two cells, an epibasal (anterior) and an hypobasal (posterior). Each of
+
+![]() A. A vertical section of an isolated embryo (x 300). B, median longitudinal section of an older embryo, showing the apical cell of stem and root. C, transverse sections of an embryo, showing the apical cells of stem and root. In the first root-cap cell has not yet been cut off.
+
+Fig. 216. — A, B, Gomondo Claytoniana. C, O. cinnamomea. A, vertical section of an isolated embryo (× 300). B, median longitudinal section of an older embryo, showing the apical cell of stem and root. C, transverse sections of an embryo, showing the apical cells of stem and root. In the first root-cap cell has not yet been cut off.
+
+these is next divided by a transverse wall into two usually equal parts, and this establishes the primary organs of the sporophyte. Of the epibasal quadrants, the outer one gives rise to the epidermis, or primary leaf; the inner one, the stem- apex. Of the hypobasal quadrants, the outer gives rise to the primary root, the other to the foot.
+
+These and Gomondo'sollen'sollen quadrants walls are thin octant-walls, which are not always exactly met in practice; this being especially the case in the root-quadrant, where one octant is usually noticeably smaller than the other. Each octant is a tetrahedron, and the next divisions in all of them are parallel to the lateral faces of the octants; that is to say, they pass through one side and leaf octants which assume the function of apical cells for these organs.
+
+PTERIDOPHYTA
+
+In the foot, the apical growth is of very brief duration, and the divisions do not show any definite succession.
+
+Root. — In the root-quadrant, the larger of the two octants at once assumes a globular form, while the smaller one undergoing very little further growth. After one or two series of lateral segments, a periclinal wall cuts off the first cell of the root-cap, and thenceforth there are four series of segments, as in the roots of the mature sporophyte.
+
+Cotyledon. — The primary leaf or cotyledon behaves at first much like the root. One of the octants develops faster than the other, and the growth is also apical ; but, of course, no cap-sils are formed, and later on the terminal apical cell is replaced by a two-sided one, and the leaf begins to assume its characteristic flattened form.
+
+The establishment of the separate growing points in the embryo soon causes a change in the mode of development. The young plant assumes the globular form found in the early stages. Growth is rapid in both root and leaf, and these presently break through the overlying tissue of the gametophyte. The root turns downward and penetrates the earth, and then grows outward, extending itself into a long, flattened blade to the light-rays. So soon as this is accomplished, the young sporophyte, which has hitherto obtained its nourishment from the gametophyte by means of the foot, now is able to live independently, and leaves behind it the gametophyte soon dies, leaving the sporophyte rooted in the ground.
+
+The cotyledon in most Ferns is fan-shaped (fig. 217), due to an early dichotomy of the leaf, which occurs several times.
+
+Of the two stem-octants, one becomes at once a primary apical cell of the permanent stem, the other develops into the second leaf, whose growth is much like that of the cotyledon, but which becomes more elongated.
+
+During its early growth, the embryo Fig. 217. — Osmunda Claytoniana.
+is protected by the enveloping tissue of the archegonium venter, which forms a calyptra like that found in the Bryophyta.
+
+Tissues of the Embryo. — The young sporophyte is composed of perfectly uniform parenchymatous cells. At first, therefore, there soon becomes evident a separation of the tissue elements into definite tissue systems. A single layer of epidermal cells is generally evident at an early period, and somewhat later the axis of each of the primary organs shows a strand of elongated cells, especially
+
+358
+
+254
+BOTANY
+
+conspicuous in the root and leaf. These are at first composed of thin-walled elements (proamnium), but later some of them begin to show the characters of the elements found in the older vascular bundles - these being met with for the first time in the young sporophyte, and are known as the primary vascular bundles. These are spiral or reticulate tracheids, which appear near the junction of the young bun-
+dles in the middle of the embryo, and develop from this point toward the apex of the shoot.
+
+**Bundled Sporophytes.** The completed vascular bundle of the young stem shows a normal cuticle on its surface, while those cells which have the scalariform markings found in the tracheids of the older stem also contain perfect sieve-tubes. In rows of cells forming the phloem, but at this stage perfect sieve-tubes cannot be made out. The xylem, however, or bundle-ducts, is also much less evident than in the older sporophyte.
+
+The tracheid tissues of the cotyledon is composed entirely of spiral tracheids, and, like the stem-bundle, the stem-tissue is also spiral. The bundle of the primary root is "monarch," i.e., there is a single strand of tracheids running through it. In the secondary root, however, the other elements of the bundle are arranged in two layers.
+
+**Ground-Tissues.** The tissues lying around the vascular bundles is usually known as ground-tissue, though it remains very much like the original parenchyma, but in the lamina of the leaf it is known as mesophyll, which is the principal green tissue of the plant, and its spaces communicate with those of the epidermis by means of the stomata developed in the epi-
+dermis.
+
+THE MATURE SPOROPHYTE
+
+The sporophytes of the various Ferns differ much in size. In some of the Hymenophylleaceae there is a slender creeping stem with up to 30 centimetres in length. Some of the Cyatheaceae are Tree-Ferns with straight stems ten to fifteen metres long and leaves five to five metres long. Ferns of temperate regions usually have a subterranean stem, which forms a bulb upon which adventitious buds may be developed from the old leaf-bases. A conspicuous case of this adventitious budding is
+
+![]() Fig. 218.--Adventitious bud.
+
+255
+
+PTERIDOPHYTA
+356
+
+seen in Struthiopteris, where numerous stolons develop from the old leaf-bases.
+
+The Stem
+
+The growth of the stem, in the typical Ferns, is due to the division of a single tetrahedral apical cell, which is unbranched stems is the direct descendant of the original stem-quadrant of the embryo. The segmentation of the apical cell is usually slow, and it is generally impossible to distinguish the extension of the leaves and lateral branches to the primary segments of the stem.
+
+Early divisions in the young segments separate a central cylinder, in consequence of which the vascular bundles and pith (when present) are delimited from the cortex. In case there is a single axial bundle, the stem is "monostelic"; if more than one vascular bundle is present, the stem is "polystelic." The ground-tissue may remain permanently parenchymatous or become sclerenchymatous. This condition is characteristic of the stems of many Ferns. The typical sclerenchyma (Fig. 221) is made up of cells with very thick striated and pitted walls of a golden or dark-brown color.
+
+Watermarked by the presence of a hollow network within which lies the pith. The spaces between the bundles are the "foliar-gaps," and it is at these
+
+![]()
+A-C. Adiantum emarginatum.
+A. longitudinal section of stem-apex (× 20); z, apical cell; L, young leaf.
+B. apex of the same (× 180).
+C. cross-section of young apex (× 180).
+D, young leaf of Struthiopteris Germarii, showing apical cell.
+
+
+Fig. 218.
+
+256
+BOTANY
+
+points that the bundles are given off to the leaves. The bundles are usually concentric in structure, but in the Ophioglossaceae and Osmon-
+
+![]() A cross-section of a vascular bundle from the rhizome of Pteridium aquilinum. A, section; 7, a stem vessel. B, part of two large scalariform tracheids. C, section of Struthiopteris gemmata (× 200). (A, B, after AYRISON.)
+
+dacees they are truly collateral. In some of the larger species of Botrychium there is a genuine secondary growth, with a true cambium.
+
+In the ferns there is no true cambium, but the leaves are derived from the typical Diostyledons or Conifers. In the typical Fern (Fig. 220) a section of a stem-bundle appears circular or oval and is separated from the ground-tissue by a well-marked bundle sheath or endodermis, composed of cells with radial walls. The endodermis is the innermost layer of the cortex. Within this are one or two layers of cells forming the "Pteridium" type which is made up of large prismatic tracheids, with conspicuous narrow transverse pits—the "scalariform" elements which are typical of the
+
+![]() Fig. 221.—Atrocarus serratus, oecophyllum from the rhizome, showing the nature of the cell-walls and pits (× 200).
+
+PTERIDOPHYTA
+257
+
+Ferns. Two strands of much smaller tracheids, with spiral or reticulate thickenings, occupy the foot of the elliptical section. These are the primary tracheids, "Protoxylem," and from these the develop-ment of the trachey tissue proceeds centripetally.
+
+The phloem, which completely surrounds the xylem, is composed of elongated, flattened cells, some of which are developed into sieve-tubes. These have a single large lumen upon their surface.
+
+Vessels, i.e., tracheary elements composed of several fused cells, are rare in the Ferns.
+
+The Leaf
+
+Where the stem is prostrate, leaves are developed upon the dorsal side only. Where it is upright, the leaves usually form a crown at its summit. In most cases, the stem is erect, and the growth of the leaf is essentially apical, generally from a two-sided cell. In Osmunda the apical cell of the young leaf is basipetal. Later the leaf is chiefly basal.
+
+The segmentation of the apical cell is much like that of the stem, and the development of the trachy tissues is accomplished in much the same way, and takes place very early.
+
+The leaves in most young Ferns are dichotomously branched, but this is not usually the case in the mature leaf, although it may be; e.g., species of Asplenium, Adiantum pedatum, etc. Much more commonly the leaves are pinnae divided, and the branching occurs by secondary divisions corresponding to the two series of segments of the apical cell.
+
+The growth of the leaf is very slow in many Ferns, especially those of cooler regions, where it often takes three years for the com-plete development of a leaf. The first year's growth consists in the formation of a shoot from which will grow two or three complete series of leaves, representing as many seasons' growth. The lamina remains rudimentary until the season preceding its expansion, when it rapidly expands and becomes fully developed during the following growing season, and is ready to expand very quickly in the following spring. This accounts for the extraordinary rapidity with which the leaves of many Ferns expand in the spring or early summer.
+
+![]() A diagram showing a fern leaf with dichotomous branching.
+![]() B A B diagram showing a fern leaf with dichotomous branching.
+![]() C C diagram showing a fern leaf with dichotomous branching.
+
+Fig. 222.—A. H. Struthiopteris Ger-manica (L.) Schott. Young sporophyte, showing dichoto- mous venation (× 3). C. Woodwardia radicans (L.) Swartz. Young sporophyte (× 3).
+
+258
+BOTANY
+
+The early growth of the leaf is much stronger upon the outer side, so that most Ferns show the marked inward rolling of the leaf which is so characteristic of these plants. In the Ophioglossaceae, how-
+ever, the young leaves are usually folded straight in the bud.
+
+A few Ferns, e.g. Scolopendrium, Asplenium niaus, etc., have simple leaves, but in many other cases, especially in the Polypodiaceae, the leaves of many Tree-ferns being among the most complex and beauti-
+fully segmented known. The leaf commonly has a well-marked stalk (*Stipe*), which when young is often covered with thin, shafty scales or *"Pales,"* and these sometimes are tipped with a glandular cell.
+
+![]() A. A section of a leaf cutting across a vein; st., section of a stoma; m., mesophyll (× 300). B, section of young sorus (× 75).
+
+Fig. 223.—Polypodium vulgare. Cross-section of a leaf cutting across a vein; st., section of a stoma; m., mesophyll (× 300). B, section of young sorus (× 75).
+
+Hairs are less common, but occur upon some Ferns. They are espe-
+cially conspicuous upon the young leaves of *Osmunda cinnamon.*
+
+Veination. — The venation of the leaves is usually pinnate, but the ultimate divisions are generally dichotomous. Sometimes connect-
+ing veins are present between the primary veins (Fig. 222). The
+venation is of some importance in classification.
+
+Epidermis. — The epidermis of the leaf is composed of flat cells with strongly undulating outline, and, unlike the epidermal cells of most vascular plants, they are often thickened at their bases. Usually developed upon the lower epidermis only, but may occur upon the upper surface in some instances. The Hymenophyllaceae differ from
+the other Ferns in having the lamina of the leaf reduced to a single
+
+PTERIDOPHYTA
+259
+
+layer of green cells, and of course in these, stomata are absent. The development of a stoma (Fig. 224) in the Polypodiaceae is preceded by the formation of a U-shaped wall in a young epidermal cell. Within the cell this wall becomes the mother-cell of the stoma. Below the stoma is developed an air-space, which communicates with those between the very loose cells of the chlorophyll. The guard-cells of the stoma are filled with chlorophyll-granules, and probably bear some relation to the opening and closing of the pores between the guard-cells, this being de-
+![]()
+A.
+B.
+C.
+D.
+St
+
+
+Fig. 224. - *Adiantum emarginatum*. Development of the stomata (*×30*): v., accessory cell; st., mother-cell of stoma.
+
+pendent upon light. The causes of the movements in the guard-cells are changes in their turgor, which are supposed to be due to the development of certain soluble substances in these cells under the influence of light. Beneath the upper epidermis the green cells are often closely arranged forming a *Chlorophyll Layer* (Plate XXVII).
+
+**Vascular Bundles.** — The vascular bundles of the stipe and larger divisions of the leaf closely resemble those of the stem, with which they are joined. The small bundles in the finer veins are usually collateral, but lying upon the upper side.
+
+The ground-tissue of the stipe often shows a large development of
+
+260
+BOTANY
+
+sclerenchyma. It is this tissue which gives the polished black appearance to the leaf-stalks of such Ferns as Adiantum.
+
+State-fern leaves, with their persistent uppermost lamina, are not uncommon. These are especially conspicuous in Struthiopteris, where they form, with the persistent bases of the foliage leaves, a complete covering for the rhizome. In many Tree-ferns, and the Marattiaeeae, the base of the leaf-stalk is provided with a naked scar upon them. In the Marattiaeeae the base of the leaf-stalk is provided with large stipules which are usually wanting in Ferns.
+
+![]() A diagram showing the development of the root.
+Fig. 25.--Difficultus emarginatus. Development of the root. A, longitudinal section of root Apex. B-E, series of transverse sections (× 300); a, apical cell; b, septate wall; en, endodermis.
+
+Trichomes.--The palae and hairs covering the young parts are undoubtedly protective. Where they develop mucilage-glands, their importance in preventing loss of moisture is sufficiently apparent.
+
+The Root
+
+The primary root of the sporophyte is of limited duration, and is soon replaced by others which continue to develop as long as the sporophyte lives. The roots always arise near the base of the leaves,
+
+PTERIDOPHYTA
+261
+
+and in some of the Tree-ferns form a thick matted mass completely covering the stem. The roots arise endogenously, the apical cell being derived from a cell of the endodermis of the vascular bundle of the stem, which finally breaks through the overlying tissues of the stem and leaf-base.
+
+Secondary roots are found in most Ferns, developed laterally upon the larger roots. These rootlets (Fig. 226) always arise from a special rhizogenium, which is an endodermal cell opposite the primary root. When the roots are dichotomous, as in the Polypodiaceae, there are, therefore, two rows of lateral roots develop.
+
+The "diplophyllous" ferns are especially conspicuous in Marsilia. In the rhizogenic cell three intersecting walls, enclosing a central cavity, are developed, and the latter at once becomes the apical cell of the new root. The basal cell, divided by three walls, forms a sort of pedicel connecting the rootlet with the vascular bundle of the main root, within which tissue is incorporated. The layer of cells immediately surrounding the end of the young root form what has been called "a digestive pouch" (Fig. 228).
+
+The segmentation of the apical cell of the root in the typical Ferns is extremely irregular. Segments arise off the apex by recession from the lateral faces, and corresponding to each series of lateral segments there is one cut off from the outer face, which contributes to the root-cap (Fig. 225). Each lateral segment is first divided into two parts by a transverse wall, and then each part divides again longitudinally. A section of the root-t Apex shows six radially arranged cells, three of which do not extend quite to the centre. Periclinal divisions next separate a central group of cells which gives rise to the central stele, or vascular cylinder. The outer cells later become separated into the cortex and epidermis.
+
+The cap segments divide first by intersecting vertical walls into four cells, which undergo repeated divisions and form the regular layers of the root-cap. Each layer of cells divides once by periclinal walls, so that two layers of cells arise from each primary cap segment.
+
+![]() Pyrus Cretica. Origin of lateral rootlet from the endodermis of the root (after Hutton).
+p.
+
+302
+BOTANY
+
+The innermost layer of the cortex forms the endodermis, or the bundle-sheath, whose radial walls are usually folded, giving the appearance, in transverse section, of dark spots. From special cells of this layer arise the root-hairs.
+
+The root-bundle, as in other vascular plants, is of the radial type. In the greater number of Ferns the bundle is "disarct", i.e. there are two groups of xylem alternating with as many phloem masses. Monarch roots occur in *Ophryococcus* edulis. *Barychloea* *Pryeri* has usually tetarch root-bundles, and in the larger roots of
+
+![]() A. B. C. D. E. F. G.
+
+Fig. 277. — *Polypodium foliatum*. Development of sporangium. A-E, from fresh specimens (× 400). F, G, microtome sections (× 300). B, C, E, optical sections; f, apical cell.
+
+Marattia and Angiopteris, the number of xylem and phloem masses is much greater.
+
+Between the endodermis and the outer xylem and phloem elements which it encloses, there is a layer of tissue, usually a single layer of cells, the pericycle. As in the bundles of the stem, the primary xylem-elements are small spiral or reticulate tracheids, and the secondary xylem consists of scalariform elements developed toward the centre of the bundle. The structure of the phloem is much like that in the stem-bundles.
+
+The cortical part of the root is composed in part of parenchyma, but the inner portion usually shows a greater or less development of heterotonymy.
+
+303
+
+PTERIDOPHYTA
+263
+
+The Sporangium
+
+The formation of spores may not occur for many years after the sporophyll has been formed, and in some cases the sporophylls which may or may not differ from the foliage leaves, the sporangia are developed. The most general type is that of Ophioglossum (Fig.
+232). Here the sporogenous tissue arises from a hypodermal layer, very much as in Anthoceros, and the distinction between sporogenous and epidermal cells is not marked. The sporangia are large, and are discharged through a transverse cleft in the overlying tissue. In other related Ferns — e.g. Botrychium, Angi-
+opteris — the archesporium is also of hypodermal origin, but there is very early differentiation of the superficial tissue so that the sporan-
+gium projects above the surface of the sporophyll.
+
+In the most specialized Ferns, those with leptosporangia,
+the sporangium can be traced back to a single epidermal cell, and the
+stalked spore-branches of these Ferns are most characteristic structures, which are of importance in classifying them.
+
+Spore-formation. — The
+sporogenous cells in all
+cases divide precisely as in
+the Equisetaceae, into four
+spores. These may be either tetrahedral in form, or sphere-quadrants resulting
+from successive divisions of the globular mother-cell. Surrounding
+the mass of sporogenous
+cells is the tapetal com-
+prising of one or more
+layers of cells, in the
+Leptosporangiatae, from the archesporium. The tapetal cells become brownish during the later stages of the spore-development,
+and the nucleated protoplasm is brought into direct contact with
+the developing spores, whose growth is doubleless in part due to
+the activity of the tapetal protoplasm.
+
+In the typical Ferns, the sporangia are usually in groups, or sori,
+
+![]() Fig. 238.—Pulmonaria falcatum. Surface view of a nearly ripe sporangium (× 175); at, spor-
+angium; at', ascus.
+84
+
+304
+BOTANY
+
+upon the back of the sporophyll. A sorus bears a definite relation to the veins of the leaf, usually beginning above one of them at its extremity (Fig. 227). At this point more active growth of the superficial tissue results in a slight elevation, or receptacle, into which sometimes passes a short branch from the vascular bundle, above which the sorus is situated. Most Leptostemonopogonateae the sorus is surrounded by a perianth covered by a membraneous outgrowth of the epidermis, the Indusium.
+
+In the Polypodiaceae, each sporangium (Figs. 227, 228) arises from a single superficial cell of the receptacle. Sometimes one or two transverse rows of cells are formed on the surface of the wall, from which the young sporangium grows, is developed. Usually the first wall in the young sporangium is nearly vertical, and is followed by two similar ones which intersect the first wall so as to include a tetrahedral angle. The first-formed wall is called the periplantinal cell and cut off several series of lateral segments, the earlier ones giving rise to the three-rowed stalk which is found in the sporangium of the Polypodiaceae. Finally a periclinal wall separates a terminal cell from the apical cell and the longitudinal growth of the sporangium is stopped.
+
+The upper part of the young sporangium rapidly increases in diameter and forms the spongyous capsule.
+
+After the formation of the periplantinal segment, it becomes the archepiromion. From it are cut off four more segments, which may divide into two layers, so that the young capsule consists of a central cell and two or three outer layers. Of this latter, the outermost periclinal layer is often divided into two parts. The inner layer or layers constituting the tapetum later have their walls broken down, and form a mass of nucleated protoplasm in which the spongyous cells lie.
+
+The primary mesophoral cell divides repeatedly, until about twelve to sixteen cells are formed. These contain very dense protoplasm and large nuclei. Finally the division walls are partially absorbed, and the spongyous cells separate completely. Each cell then divides into two daughter cells.
+
+The young spores have a thin cellulose membrane, which later becomes differentiated into an inner (intine) and outer (exine) layer. As the spores approach maturity, there is usually deposited upon their surface a thickening of protoplasmic material, protopo-
+plasm, an outer sculptured membrane, the epispore, or peritum.
+
+The wall of the sporangium consists of a single layer of large, thin-walled cells, except for the peculiar annulus, or ring of thickened cells within it (Fig. 228), and of a single layer of epispore (co-
+mium (Fig. 228), which is composed of two narrow cells between which the transverse opening occurs. The stomium is formed in the
+
+PTERIDOPHYTA 266
+
+last lateral segment of the apical cell. The inner and radial walls of the annulus cells become very much thickened, and when the ripe sporangium dries, the strong contraction of these cells acts like a spring, and the spores are thrown out with great force. When open at the stomium, the split extending far back through the lateral cells of the wall. The annulus bends far back and then returns to its original position with a quick jerk, which throws the spores for a long distance.
+
+![]()
+A: A germinating spore (× 600).
+B: Section of gametophyte, showing the foot of the young sporophyte.
+C: Spore-phyte attached to the gametophyte, pr × 2.
+D: Section of gametophyte, showing the foot of the young sporophyte.
+E: Young leaf (× 2).
+
+
+**Classification of Filicines**
+
+The Filicines may be divided into two subclasses — Eusporan-
+giate and Leptosporangiate.
+
+SUBCLASS I. EUSPORANGIATE
+
+The Eusporangiate comprise but a small proportion of existing Ferns, and show many evidences of being the most primitive members of the class. This is proved both by the characters of the gametophytes and of the sporophytes. The three orders included
+
+![]()
+Fig. 239. — *Hymenophyllum Virginianum*. A, B, germinating spore (× 600). C, sporo-
+phyte attached to the gametophyte, pr × 2). D, section of gametophyte, showing
+the foot of the young sporophyte. E, young leaf (× 2).
+
+
+206
+BOTANY
+
+here, Ophioglossaceae, Marattiaceae, and Isotaceae, are not closely related among themselves, and the affinity of the latter with any of the Ferns may be questioned.
+
+Order I. Ophioglossaceae
+
+The Ophioglossaceae differ much from the typical Ferns, both in the gameto-
+phyte and sporophyte. They constitute a small order, comprising the two
+widespread genera, Ophioglossum and Borychium, and the monotypic Hal-
+minthostachys of the East Indies.
+
+![]() C
+![]() A
+![]() B
+
+Fig. 230. — *Borychium Firpionisum*. *A.*, *B.*, *antheridia* (*× 600*). *C.*, *archegonium* (*× 600*).
+
+Gametophyte. — The gametophyte is best known in *Ophioglossum Furfuraceum*, as it is intermediate between the body of the gametophyte and always showing a ventral mass of tissue which contains an endophytic Fungus, closely resembling the "mycorrhiz" associated with the roots of many saprophytic seed-plants. The presence of this Fungus is doubtless associated with the
+saprophytic nature of the gametophyte.
+
+The sexual organs are borne upon the upper surface of the gametophyte. The
+antheridia are large and occupy a median ridge, upon whose flanks are later
+developed the archegonia.
+
+PTERIDOPHYTA
+207
+
+**Antheridium.** — The mother-cell of the antheridium (Fig. 230) divides by a transverse wall into a superficial cell which develops into the outer wall, and an inner cell which gives rise to the sporangium. The latter, according to Jeffrey (19), always divide ultimately into two layers, like the antheridium of the ferns, but not into three. The large multiciliate spermatoidae are much like those of the typical Ferna.
+
+**Archegonium.** — The archegonium (Fig. 230, C) does not differ essentially from that of the typical Ferna. It has a straight neck, which is longer than
+
+![]() A diagram showing the structure of an antheridium and an archegonium.
+A.
+B.
+C.
+D.
+
+Fig. 231. — *Hypopteris* *Fernuana*. Longitudinal section of an advanced embryo (*× 30*); *a*, stem-axon; *c*, cytoplasm; *f*, foot; *r*, root; *cot*, calyptrae. (After JEFFREY.)
+
+that of Ophioglossum, which it otherwise resembles.
+
+The Embryo. — The first division in the embryo is transverse, and the develop-
+ment of the sporophyte from the sporo-
+phyte is much later than in the more
+specialised Leptoporemangia (Fig. 231).
+This fact explains why the sporophyte,
+correspondingly long dependence of the
+sporophyte on the gametophyte, re-
+pruch the condition found in the Bryo-
+phytes. The stem and root grow from
+a specialised apical cell, and this is
+the same as that found in the same parts
+of the typical Ferna. The foot is very large,
+and the calyptra may remain for several years attached to the gametophyte.
+
+The Mature Sprorophyte
+
+The sprorophyte in both Ophioglossum (Fig. 232) and Botrychium (Fig. 233)
+has a short, upright stem which, in our native species, is subterranean. The thick, fleshy roots contain a mycorrhiza like that in the gametophyte. In some tropical species — e.g. Ophioglossum prolatus — the plant is epiphytic.
+
+![]() A diagram showing the mature sprorophyte of Ophioglossum prolatus.
+A.
+B.
+C.
+D.
+
+Fig. 232. — *Ophioglossum vulgatum.* Sprorophyte, slightly reduced; *B*, G., *C*, H., *D*, I., *E*, J., *F*, K., *L*, M., *N*, O., *P*, Q., *R*, S., *T*, U., *V*, W., *X*, Y., *Z*, Z., *a*, axon; *b*, foot; *c*, root; *d*, calyptra; *e*, sporangium cavity (*× 5*); *f*, sporangium (*× 5*); *g*, sporangium (*× 5*); *h*, sporangium (*× 5*); *i*, sporangium (*× 5*); *j*, sporangium (*× 5*); *k*, sporangium (*× 5*); *l*, sporangium (*× 5*); *m*, sporangium (*× 5*); *n*, sporangium (*× 5*); *o*, sporangium (*× 5*); *p*, sporangium (*× 5*); *q*, sporangium (*× 5*); *r*, sporangium (*× 5*); *s*, sporangium (*× 5*); *t*, sporangium (*× 5*); *u*, sporangium (*× 5*); *v*, sporangium (*× 5*); *w*, sporangium (*× 5*); *x*, sporangium (*× 5*).
+
+268
+BOTANY
+
+leaves are undivided in most species of Ophioglossum, but in the larger species of Bryorchis they are repeatedly divided, not unlike those of the true Fersa.
+The leaf-bases are developed into sheaths which completely enclose the apex of the stem. The leaves often require three to four years, or even five, for their complete development.
+
+*Speranium.* — The sporangia are borne upon peculiarly modified outgrowths of the leaf, the Sperangiophore. This has the form of a spike in Ophioglossum, but may be a simple leaf-like structure. The Basidiomycetous Sporangia are much more clearly defined than in Ophioglossum. The tetrahedral spores
+
+![]() A
+![]() B
+![]() C
+![]() D
+
+Fig. 333. — *Bryorchis viridisianum.* A, rhizome and terminal bud of a strong plant, the roots, and all but the base of the oldest leaf cut away (× 1). B, longitudinal section through a young shoot (× 10). C, transverse section through different ages; st., stem-axil. D, cross-section of the petiole (× 10). B, cross-section of rhizome (× 16). F, pith; x, wood; ph, phloem; ah, endodermis; m, medullary rays.
+
+Histology of *Speranium.* — The ground-tissue is mainly composed of parenchyma. The epidermis is thin and consists of one layer of cells. There is no development of cork. The vascular bundles of the stem are collateral, and in the larger species of *Bryorchis* form a woody cylinder, suggesting the structure of a woody stem. In *Ophioglossum* the vascular bundles are scattered and developed which causes a regular secondary thickening of the stem. The bundles of the leaves are also collateral in *Ophioglossum*, but in the large species of *Bryorchis* they approach the conoscentic type, but never so perfect a form as in the true Fersa.
+
+268
+
+PTERIDOPHYTTA
+300
+
+![]()
+A: A young sporangium (× 600).
+B: A young sporangium (× 600).
+C: An older one (× 280); all median sections; the sporogenous cells have the nuclei shown.
+D: A young archegonium (× 600).
+E: A mature archegonium (× 600).
+F: Surface view of antheridium, showing spercular cell (× 600).
+G: Free spermatocyst.
+H: Free spermatocyst.
+
+
+Fig. 254. — *Barbula* Virginianum : development of the sporangium. A, B, young sporangia (× 600). C, an older one (× 280); all median sections; the sporogenous cells have the nuclei shown.
+
+Fig. 255. — *Marattia* Douglasi : development of sexual organs. A, B, C, archegonium ; D-F, antheridium. F, surface view of antheridium, showing spercular cell. G, H, free spermatocysts, containing ripe spermatocysts. H, free spermatocyst. (A-F, × 600; G, H, × 800.)
+
+270
+BOTANY
+
+Order II. Marattiaceae
+
+The Marattiaceae include a small number of tropical forms which resemble, in their general appearance, the typical Ferns. The sporo-
+phyte may be erect or prostrate, and is usually a small plant of Marattia, where the thick, tuber-like stem is half a metre or more in diameter, with a crown of thick leaves three to four metres or more in length.
+
+![]() A, B, C, D - longitudinal, transverse sections of antheridia (× 215). C, vertical section of old antheridium showing position of the protallium (× 72); e, archeonium. D, upper part of same antheridium (× 215).
+
+Fig. 386. — *Marattia Douglasii*. Antheridia. A, longitudinal; B, transverse sections of antheridia (× 215). C, vertical section of old antheridium showing position of the protallium (× 72); e, archeonium. D, upper part of same antheridium (× 215).
+
+The Gametophyte
+
+The small, colourless sporophyte dwindles slowly, the first division occurring in about a month after the spores are shed. The gametophyte (Fig. 385) is a feathery green thallus, much like a Liverwort in appearance, and upon it are borne both antheridia and archeonia. The latter are confined to the lower side, as they are in the Ophioglossaceae; but the antheridia are on the upper side, and resemble those of the Ophioglossaceae, but the outer wall of the antheridium has been lost, and the opening is made by a small triangular opercular cell. The archegonium neck is very short.
+
+The gametophyte frequently multiplies by the formation of adventitious buds, and the young plants soon separate from the parent plant.
+
+Embryo. — As in Botrychium, the basal wall of the embryo is transverse, and the differentiation of the organs is slow, so that the embryo remains long de-
+
+PTERIDOPHYTA
+271
+
+pendent upon the gametophyte. The young stem and primary root show a single apical cell, which is probably replaced by a group of initial cells in the massive stem and root of the mature sporophyte. The cotyledon in Marattia is forked like that of the typical Ferns; but in Angiopteris and Danaea it has a much more complex form.
+
+The Mature Sporophyte
+
+All of the existing Marattiaceae are tropical. The stem in Angiopteris and Marattia is a nearly globular massive body, covered with the thick persistent stipules of the young leaves. In Danaea the stem is prostrate, but otherwise much like that of the other genera. The leaves, which are finely in texture, are smooth, and glaucous when young.
+
+Echinostegia. — As in the Ophioglossaceae, the ground-tissue is principally composed of parenchyma, but sclerenchyma (Fig. 287) occurs in a somewhat larger leaf-stalks. It may, however, be re-
+placed by thick-angled tianee (collenchyma). Compressed vascular bundles (Fig. 238) closely resembling those in the Cyatheaceae, occur mostly in the ground-tissue, and among the lower leaves; but in some species of Danaea, are of common occurrence. The vascular bundles in Danaea are concentric and not strikingly different from those of the Leptopterogynites.
+
+The Sporangia. — The sporangia (Fig. 300) are more or less completely united into a sporangiophore, which is often very large and conspicuous, but quite lost. In Angiopteris and Arachnopteris the individual sporangium can be recognized, and they bear an important relation. The sporangiophore may be tumid or constricted at its base. In Angiopteris and Marattia, it is usually lower surface almost completely hidden by the crowded syngonia (Fig. 287, B). In all cases it is attached to one side of the sporangiophore, either by a stalked sporangium, or each locus of the syngonia, open by a longitudinal slit, or pore.
+
+Of the existing genera, Marattia is cosmopolitan; Angiopteris occurs in the eastern Tropics; Kainifolia is East Indian, and Danaea is American. The re-
+cently discovered Arachnopteris comes from southern-western China.
+Fossil forms of Angiopteris and Danaea have been allied to the living Marattiaceae, and it is evident from a study of these fossil forms that the
+
+![]() A diagram showing parts of a plant.
+A
+B
+C
+
+Fig. 237. — Danaea dioica. A, sterile pinnule, attached to the winged rachis (× 1½). B, under surface of a leaf-stalk (× about 6); C, transverse section near the base of the petiole (× about 6); d, collenchyma; m, multicellular; v0, vascular bundles.
+
+271
+
+272
+BOTANY
+
+Marattiacae are much older than the leptoporangiate Ferns which have now largely superseded them.
+
+![]() A
+![]() B
+
+Fig. 396. - *Dennstaedtia.* A, transverse section of vascular bundle of the petiole (× 175); $x$, tracheary tissue; $r$, tannin cell. B, cross-section of a metaxylem-duct (× 175).
+
+SUBCLASS II. LEPTOPORANGIATE.
+
+Much the greater number of existing Ferns belong to the second division, the Leptoporangiate. These are characterized by having the sporangium the derivative usually of a single epidermal cell.
+
+![]() C
+![]() D
+![]() E
+![]() F
+
+Fig. 397. - Development of sporangium. A, R, sections of young sporangium. (After Goebel.) C, section of a nearly full-grown sporangium, show- ing persistent tapetum, $r$, and annulus, $r$ (× 75).
+
+PTERIDOPHYTA 278
+
+The lower members of the series, however, especially the Osmun-
+daceae, are to some extent intermediate in this respect between the Euparan-
+gii and the more specialized Leptosporangiatae.
+The Leptosporangiate may be divided into two orders, i. Filices,
+or hornworts, and Polypodiaceae, or ferns, the latter being thalloid or thallophytic
+Ferns. The latter develop two sorts of spores, large ones (Macro-
+spores, Megaspores) and small ones (Microspores). The megaspore gives rise to a female gametophyte, the microspore to the extremely reduced male plant.
+
+Order I. Filices
+
+The general characters of the Filices have already been given in the earlier part of the present chapter. The gametophyte is always relatively small, and is usually leafy or frond-like. The sporophyte ranges from a centimetre or less in height (Tricho-
+manes parvulum) to ten or fifteen metres (Cynopteris sp.). They are for the most part moisture-loving plants, and are sometimes genuine aquatic forms, such as the water-milfoil (Myriophyllum), and the water-fern
+(Angiopteris), —are more or less marked xerophytes. In the Tropics many species, especially among the Hymenophyllaceae and Polypodiaceae, are epiphytes. Some of these epiphytic Ferns, like Platycerium, produce a large number of aerial roots, or leaves, which serve to hold moisture, and to accumulate decaying vegetative material and dust which are utilized as sources of food.
+
+Spermatangium. — The spermatangia in the homosporous Ferns are always borne up on special structures, the sori; they are usually not much modified, although sometimes —e.g. Onoclea, Struthiopteris, *Blechnum* *spinosum*, etc. —the fertile and barren fronds are decidedly different.
+In other Ferns, like Lygodium and Anemia, special fertile leaf-seg-
+ments are produced by means of a special structure called a tetra-
+hedral archesporial cell, and the ripe spermatangium has its wall composed of but a single layer of cells. An annulus is always present, and the form and position of the annulus are the most im-
+portant characters for distinguishing the various families of Filices.
+
+Classification. — The Filices may be divided into the following families: 1. Osmundacea; 2. Gleicheniacea; 3. Matteoacea;
+4. Schizaeacea; 5. Hymenophylaceae; 6. Cyatheaceae; 7. Ptereri-
+acea; 8. Polypodiacea.
+
+Family I. Osmundacea
+
+The Osmundaceae are the lowest of the Leptosporangiatea, and in the charac-
+ters of both gametophyte and sporophyte are to some extent intermediate between the typical Leptosporangiatea and the generalized Euparan-
+gii. The gametophyte is large and not unlike that of the Marattiae. The character of
+
+7
+
+274
+BOTANY
+
+the sexual organs, and the early stages of the embryo, also approach the euphorangiate type.
+
+The sporophyte shows certain analogies with both the Marattiacae and Ophioglossaceae, but differs from them in having the vascular bundles of the stem, which are collateral instead of concentric as in the typical Ferns. The leaves are circinately coiled as in the Marattiacae.
+
+The rhizome (Fig. 341) may be hermaphrodite, unaltered or but slightly modified sporophyte, e.g. Tmesis, Leptopteris ; or special portions of
+
+![]() A
+![]() B
+
+Fig. 340. - A, Osmunda Cilipesoides. Sporophyll, natural size; ep., spo- rangle. B, section of the rhizome of G. revoluta showing the arrangement of the vascular bundles (× 5). (B, after J. H. Wood.)
+
+the leaves may be completely covered with sporangia, as in Osmunda (Fig. 340). Osmunda ciliopseoides has the whole sporophyll covered with sporangia. The sporangia are sessile and are arranged in two rows on each side of the rhizome, one side of the dehiscence is longitudinal. The sporangium in its earlier stage is much more massive than that of the typical Leptosporangiate, and cannot be referred to any other group.
+
+The apical growth of both stem and root is less regular than in the higher Lepto- sporangiates, and in this respect also the Osmundaceae suggest the Euphorangiates.
+
+![]() A
+![]() B
+
+Fig. 341. - Osmunda ciliopseoides. Bipe sporangium. A, from above. B, from in front; r., annulus (× 45).
+
+275
+
+PTERIDOPHYTA
+
+The Osmundaceae are probably old forms which have largely disappeared. At present about a dozen genera are known. Of these, three species of Osmunda occur in this section of the United States, but none are found on the Pacific coast. The other genera, Todea and Leptopteris, belong to the southern hemisphere.
+
+**Family 2. Gleicheniaceae**
+
+The Gleicheniaceae comprise about twenty-five species of Ferns, principally confined to the Tropics, but extending to the extreme southern part of South America. Except for the monotypic *Stro-
+matopteris* *mondiformis*, they all may be included in the genus *Gleichenia* (Fig. 242).
+
+Ph
+
+**Fig. 243.—*Gleichenia* dichotoma.* A*, pinnae, showing the position of the sori; *s* (= 4); *B*, leaf, showing the venation; *r* spores (*× 58*). *D*, vascular bundles of the petiole and stem of *Gleichenia*; *en* the dark brown represents the xylem; *ph*, phloem; *en*, endodermis. (*D*, after FORMAUR.)**
+
+Gametophyte.—The gametophyte is intermediate in character between that of Marchantia and the higher Lepidostomataceae.
+
+Sporepyte.—The sporophyte of *Gleichenia* has a slender creeping rhizome, which is monosolic. The leaves are in most species dichotomously branched, and have an adaxial vein with lateral veins radiating from it. The fronds grow over shrubs and trees, often forming almost impenetrable thickets. Very often
+
+![]()
+A: Pinnae showing the position of the sori.
+B: Leaf showing the venation.
+C: Vascular bundles of the petiole and stem of *Gleichenia*.
+D: Xylem (dark brown), phloem (ph), and endodermis (en).
+
+
+276
+BOTANY
+
+adventitious buds are developed, especially in the forks of the leaf. The tumescences are very much like those of the typical Leptoporegoniaceae.
+
+The sporangia are sessile, with a broad, oblique annulus (Fig. 243), and open longitudinally. They are grouped in small, naked spots, upon the lower surface of unmodified leaves.
+
+**Family 3. Matoniaceae**
+
+Sometimes included with the Gleicheniaceae is the peculiar genus Matonia, represented by two species from the Malayan region. They differ from the Gleicheniaceae in the sporangia, which are more like
+
+![]() A: A cluster of spore-producing structures.
+![]() B: A section of a sporangium showing the spores.
+![]() C: A cross-section of a sporangium.
+![]() D: A cross-section of a petiole.
+
+Fig. 243.—*Lycopodium japonicum*. *A*, pinnae (*× 5*); *a*, the sporangial segments.
+*B*, section of a sporangium showing the spores; *b* (*× 14*). *C*, sporangium (*× 68*); *r*, annulus. *D*, cross-section of petiole (*× 68*).
+
+those of the Polypodiaceae or Cyatheaceae. The sorus is covered by a peculiar shield-shaped indusium. The Matoniaceae are the last remnants of a family which was abundant in the earlier Mesozoic formations.
+
+**Family 4. Schizomaceae**
+
+The Schizomaceae, which include about one hundred species, like the Gleicheniaceae are mainly tropical in their distribution, but there are several exceptions. In the Atlantic States, two species, *Lycopodium palmaeum* and *Schizaea pusilla*, occur, and in Texas there are several species of Anemia.
+
+PTERIDOPHYTA
+277
+
+Gametophyte. — The gametophyte does not differ essentially from that of the
+Polypodiaceae, and so far as it is known, the embryo also is very similar.
+Sporophyte. — The sporophyte is a simple, erect, rhizome, from which are sent up the leaves. The latter in Lygodium have an unlimited spreading growth, and the leaf-stalks twine so that those known as climbing Ferns. The leaves are usually modified, either the whole leaf being strongly contracted, e.g. *Solomon's Seal*, *Lysimachia*, or the leaflets being long-stalked, as in *Lygodium* and *Anemia*. In the latter genus, the lower pair of leaflets are long-stalked. Some species of *Anemia* are also characterized by the peculiar form of their stoma, in which one cuts out the mother-cell circularly, so that the stoma lies in the middle of an epidermal cell.
+
+![]()
+A. B.
+C. D.
+
+
+Fig. 364. — A, *Hymenophyllum recurvum* (× 5). B, *Trichomanes peruvianum* (× 5).
+C, T. *opteridifolium* (× 5). D, 1st instar more enlarged; 2, section of stomata,
+showing the nerve.
+
+Sporangium. — The sporangia (Fig. 245. C) are large, and possess a terminal annulus, which in Lygodium and Anemia forms a conspicuous cap of thickened cells. This cap may be wanting in some species of *Hymenophyllum*, or there may be a special indusium for each sporangium (*Lygodium*).
+
+**Family 5. Hymenophyllaceae**
+
+The Hymenophyllaceae are especially characteristic of the moist mountain forests of the Tropics, where their exquisite filmy fronds sometimes quite cover the trunks of trees with their graceful drape. A few species extend beyond the Tropics, but only two species, and these extremely rare occur within the United States. There are two genera, *Hymenophyllum* and Trichomanes, each com-
+
+278
+BOTANY
+
+prising about eighty species. A third monotypic genus, *Loxosoma*, is sometimes included in the family.
+
+**Gametophyte.** — The gametophyte is very different from that of other Ferns, probably due to the excessively moist localities in which they usually grow, which induce an excessive vegetative development, so that sometimes great
+
+![]() A
+![]() B
+![]() C
+
+![]() D
+![]() F
+
+![]() E
+![]() F
+
+Fig. 365.—*Trichomanes cyrtothecum*. Development of the sporangium (× 225). *F.*, horizontal section of a nearly ripe sporangium; *r*, annulus.
+
+mate of the prothallus are met with, which may easily be mistaken for Liver-worts. In many species of *Trichomanes*, the prothallium is an extensively branched structure, but in *Pleurozium*, which belongs to the same phylum, it resembles the prothallium of the *Polypodiaceae* in its earlier stages, and always is flat, but may branch extensively and reach a length of several centimeters. Special gametes are common in these plants and permit a rapid
+
+PTERIDOPHYTA
+279
+
+multiplication of the gametophyte, independently of the spores. The sexual organs are similar to those of the Osmundaceae.
+
+Sporophytes of the genus *Cibotium* (Cibotioideae) is usually small, and is characterized by the extreme delicacy of the leaves. The slender, creeping stem is armed with minute, sharp-pointed, recurved spines. The leaves are much like those of the typical Ferns, but show much variation in the number of xylem-masses. The plants are very generally epiphytic, or grow upon rocks exposed to the spray of mountain streams or canyons. This adaptation to an extremely moist atmosphere is seen in the leaves, which, with few exceptions,
+
+![]()
+A: A pinnule with seta (× 3).
+B: Sorus, with two-valved indusium (× 9).
+C: Sporangium (× 80).
+D: Phyllaparaphysis (× 80).
+r: Leaf.
+
+
+Fig. 266. — *Cibotium Mouzii*. *A*, pinnule with seta, × (× 3). *B*, sorus, with two-valved indusium (× 9). *C*, sporangium (× 80). *D*, phyllaparaphysis (× 80).
+
+consists of a single layer only of green cells stretched between the veins. This gives the leaves a delicate appearance, and is characteristic of the genus *Sporanthum*. The sporangia (Fig. 241) are borne at the ends of the veins upon a receptacle which in *Trichomanes* becomes extremely elongated. The stem is unarmed except for a few scattered spines on its lower surface. The tetrahedral spores at maturity contain chlorophyll.
+
+**Family 6. Cyatheaceae**
+
+The Cyatheaceae are Tree-ferns which structurally closely resemble the Polypodiaceae, from which they differ mainly in the oblique annulus of the sporangium and the cup-shaped indusium (Fig. 246).
+
+![]()
+A: A pinnule with seta (× 3).
+B: Sorus, with two-valved indusium (× 9).
+C: Sporangium (× 80).
+D: Phyllaparaphysis (× 80).
+r: Leaf.
+
+
+280
+BOTANY
+
+The gametophyte is much like that of the Polypodiaceae, but very often develops upon its upper surface characteristic bristles.
+
+The Cyatheaceae are the most imposing of all existing Pteridophytes, and their Palm-like trunks and crowns of gigantic leaves are among the most conspicuous of the tropical mountain-flora.
+About two hundred and fifty species have been described, some of which are found only in the southern hemisphere. The most important genera are Cyathea, Aleocharia, Dicksonia, and Hymenophyllum.
+
+Family 7. Parkeriaceae
+
+The single representative of this family, usually included with the Polypodiaceae, is a peculiar aquatic Fern, *Ceratopteris thalictroides*, widely distributed in the Tropics, and reaching our limits in Florida. The annulus is sometimes completely suppressed.
+
+Family 8. Polypodiaceae
+
+The Polypodiaceae include a very large majority of all existing Pteridophytes, and are the most modern representatives of the sub-kingdom. The greater number of Ferns of cooler regions are Poly-
+podiaceae, and occasionally, as in the case of *Pteridium aquilinum*,
+
+![]() A illustration showing a fern frond with a spore-producing structure (sp) at the base.
+Fig. 361. A. *Polypodium vulgare*. Fern with sp. × 4; natural size. B. *Parviloma* *fasciculatum*. C. *Apolymium filix-femina* × 5.
+
+![]() A illustration showing a cross-section of a young fertile pinnule (× 30). s, annulus.
+Fig. 368. A. *Lepidium spinulosum* × 3½. B. *Struthiopteris Germanica*, cross-section of young fertile pinnule (× 30); s, annulus.
+
+PTERIDOPHYTA
+281
+
+they occur in numbers enough to be a conspicuous feature of the vegeta-
+tion. The general characters of the family have already been dis-
+cussed, and the family is an extremely natural one. The differences
+between the various species are secondary in nature, depending
+upon the position of the sor; the character of the indusium, etc.
+(Figs. 247, 248). About one hundred and sixty species occur within
+the United States.
+
+CHAPTER IX
+
+PTERIDOPHYTTA (Concluded)
+
+ORDER HYDROPTERIDINELE
+
+Tunas are two families of heterosporous Ferns, which although not closely related to each other, are evidently allied to the other leptosporangiate Ferns. These have been put together in the order Hydropteridinaceae, or Water-Ferns, as they are all aquatics.
+
+They agree in the general characters of the sporangium, and in producing a single very large macrospore in each macroprogenium. The Hydropteridines fall into the two very natural families, Salviniaeae and Marilleanae.
+
+**Family 1. Salviniaeae**
+
+The Salviniaeae are small floating plants which show very little superficial resemblance to the Filices, from which they have been derived. Their internal structure is simple, and the development of the sporangium are very much like those of the typical Ferns. The character of the sporangium and its position suggest the Hymenophyllaceae, to which the Salviniaeae may possibly be remotely related.
+
+There are two genera, Salvinia and Anola. The former is represented in a few places in the United States by the European species, *S. natans* (Fig. 249, D, E), but there is some question whether it is really indigenous here. It was introduced from Europe by A. *Caroliniana*, and on the Pacific coast by the larger A. *Microlodis* (Fig. 249), both species extending into South America. A third species, *A. pinada*, has been introduced in some places, with the Japanese *Salvinia* (Fig. 249, C). This is a small plant with a slender horizontal stem, floating upon the surface of quiet water. Two or four rows of dorsal leaves quite conceal the stem. The dorsal leaves in Salvinia are oval; in Anola, each leaf has two lobes, dorsal and ventral.
+
+The lateral branches arise from the base of the stem upon the ventral side of the stem two rows of leaves which are divided into many slender, rootlike segments, functionally replacing the true roots (Fig. 249, D, f). In Anola roots are developed. In both genera more or less conspicuous hairs are found upon the leaves. Lateral branches are freely produced, and by the detachment of 263
+
+PTERIDOPHYTA
+283
+
+these the plants often increase very rapidly, and completely cover the surface of the water over large areas.
+
+**Apical Growth.** — The stem-apex is extended beyond the youngest leaves, in the form of a slender cone, which is bent upward in *Anella*. It grows by an apical cell, from which two rows of segments are produced. Each segment divides into a dorsal and a ventral cell so that a transverse section made just back of
+
+![]()
+A: A-C, *Anella filicoides*. A, *sporephyte* (× 5). B, branch with two microsporangial sporocarps (× 6). C, macrosporangial, me., and microsporangial, me., sporocarps (× 10). D-E, *Salvinia natans*, id. (× 3), dorsal view (× 3), ventral view (× 3). F-G, *Anella filicoides*, section of young macrosporangium enclosed in the indusium, id.; n., nucleus. A, dorsal view; B, ventral view.
+
+
+Fig. 369. A-C, *Anella filicoides*. A, *sporephyte* (× 5). B, branch with two microsporangial sporocarps (× 6). C, macrosporangial, me., and microsporangial, me., sporocarps (× 10). D-E, *Salvinia natans*, id. (× 3), dorsal view (× 3), ventral view (× 3). F-G, *Anella filicoides*, section of young macrosporangium enclosed in the indusium, id.; n., nucleus. A, dorsal view; B, ventral view.
+
+the apex shows a dorsal and two ventral cells. From the former the dorsal leave arises, from the latter the root (or, in *Salvinia*, the ventral leave) and the lateral branches.
+
+The stem is covered by an axial vascular bundle, like that of the stem in the Hymenophyllaceae and Schismataceae. The bundle is typically concentric in structure. As in all aquatics, large air-spaces are developed, forming a series of longitudinal canals separated by this plates of cells.
+
+284
+
+284
+BOTANY
+
+The Leaf.—The leaves in Salvinia are arranged in alternating whorls of three, so that there are four rows of dorsal leaves and two of ventral ones. In both Salvinia and Azolla, the leaves are borne on internodes with leaf-bearing ones, thus dividing the stem into nodes and internodes.
+
+The dorsal leaf in Salvinia is composed of large air-chambers, arranged in two layers, separated by a thin layer of parenchymatous tissue, which do not differ essentially from the epidermal cells. In Azolla the ventral lobes of each leaf bear a single row of elongated cells, which are surrounded by a layer of elongated loosely placed mesophyll, bounded by the epidermis. There is always found in the dorsal leaf of the leaf a large cavity, communicating with the exterior, and containing a large number of gas-bubbles (Fig. 240, A). The Anabema grows about the apex of the shoot, and a filament creeps into the cavity of each young leaf as soon as it is formed. Stomata are developed upon the upper surface of the leaves.
+
+The leaf in Salvinia grows from a two-sided apical cell, as in the typical Ferns, but this is not the case in Azolla.
+
+Root.—The root is composed of external cells, instead of endogenously. The first outer root cap-epigament develops into a sheath, which encloses the root, and only another cap-epigament is formed. Otherwise the root is like that of the typical Ferns.
+
+The Sporangium.—The sporangium (Fig. 240), which in their development correspond to those of other Leptosporangiate, arise from special leaf-segments. The sort are borne upon the ventral leaf in Salvinia and replace the terminal leaf of the leaf in Azolla. The corona is completely enclosed by the innermost cells, cup-shaped at first, but finally becomes globular and completely closed at the top. In their position and the form of the indusium, the sporangia of Salvinia resemble those of Azolla. The formation of the indusium about the single macrosporangium of Azolla strikingly resembles the development of the integument about an ovule.
+
+The macrosporangia and microsporangia are in separate series. The former are less numerous, and in Azolla reduced to a single one. The sporangia arise from a central receptacle, or placenta, and in Salvinia the microsporangia are borne at the ends of the divisions of a branching stalk.
+
+The early divisions of all the sporangia are alike. From the central tetrahedral antheroblasts arise off the initial cells, as in the typical Ferns, and the central cell then divides into eight or ten into sixteen sporogenous cells, all of which divide. In the microsporangium, all of the sixty-four young spores develop simultaneously; but they grow more slowly than those of Azolla, and finally occupy the whole of the sporangium, destroying it entirely. In Salvinia there is no evidence that the integument is not used up in the development of the macrospore, but part of it persists in the form of peculiar epispore appendages, which are especially well developed in Azolla. These appendages do not nearly fill the cavity, but are imbedded in a foamy mass of hardened protoplasm derived from the tapetum. This is divided into several parts; or "massules," in Azolla; and upon these massules are developed cutinous anisochelae.
+
+![]() A diagram showing the structure of Salvinia.
+
+PTERIDOPHYTA 285
+
+appendages, Glochidia (Fig. 360). The glochidia attach the massula to the epipodic outgrowth of the macrospore, and thus facilitate fertilization, as the germinating microspores are thus kept near the macrospore.
+
+The wall of the macrospore consists of two layers of cells, which in Salvinia are partly separated by air-spaces. The absence of an annulus in the sporangium is to be explained by the aquatic nature of these plants.
+
+In Azolla the infection of the plant by the Anabema always associated with it, occurs while the macroperangium is developing. The Anabema filaments enter the young sporocarp and remain dormant until the germination of the macrospore begins; and by the time the young sporophyte emerges from the gametophyte, the Anabema is in condition to infect it.
+
+The Gametophyte
+
+The ripe sporocarps, with the enclosed sporangia, fall away from the sporophyte, and after a period of rest germinate. The spores are set free by the decay of the wall of the sporangium, and in Azolla the massula separate and soon attach themselves to a new gametophyte. In Salvinia, however, when a rudimentary prothallus is developed, consisting of a large basal cell, from which a smaller rhizoidal cell is later cut off, and a terminal cell, from which the
+
+![]()
+A. A. massula with enclosed microspores.
+B. A. germinated massula.
+C. A. cross-section of an antheridium.
+D. E. two cross-sections of an antheridium.
+
+
+Fig. 360. *Azolla filiculoides*. A. massula with enclosed microspores, sp.; pl. glochidia (× 300); B. germinated massula; scale gametophytes (× 560); a, opercular cell. C, E, two cross-sections of an antheridium (× 760).
+285
+
+266
+BOTANY
+
+anarthidium is formed. The latter develops eight sperm-cells, which are in two groups, and are sometimes considered to represent two anthidia (Fig. 250). The spermatocoids are multiciliate, like those of the typical Forma.
+The (spore) wall is thin, and consists of a single layer of cells (episperm), which in Anzia is curiously sculptured and provided with fine hairlike outgrowths, to which the glodia become attached. In Anzia also, the pointed apex of the spore is directed towards the growing gametophyte (Fig. 251). The spore is filled with dense granular cyto-plasm, and the nucleus lies in its upper part. The first division of the nucleus is followed by a second one, which divides the protoplast into four parts of the spore. This becomes the prothallium, the lower cell remaining undivided, and serving as a food-supply for the developing gametophyte. In Anzia, how-
+ever, the nucleus of this large basal cell subsequently divides, but there is no cell-formation. It is not known whether this nuclear division also occurs in Salvinia.
+
+The prothallial cell undergoes rapid divisions, and forms a projecting mass of tians (Fig. 251), which develop chlorophyll, especially in Salvinia, where the gametophyte is green. In Anzia, however, the prothallial cells are similar to the homosporous Forma. The gametophyte is triangular in form, and in Salvinia two of the angles are obtuse, while in the lobes of green algae. Several anec-
+gonia, much like those of the ordinary Forma are formed, the latter being larger in Salvinia than in Anzia. The structure of the archegonium (Fig. 261,
+C) is much like that of Leptosporangiate. It is still a question whether a primary root is indicated in
+embryo.
+
+![]() Fig. 251.—Anzia filicoides. Female gametophyte and archegonium. A, B,
+longitudinal sections (× 250). C, D, anaphase (× 375). E, two transverse sec-
+tions of archegonium (× 375). F, section of macrospore
+and large prothallium (× 68); &c., indusium.
+
+**Fig. 251.** — **Anzia filicoides.** Female gametophyte and archegonium. A, B,
+longitudinal sections (× 250). C, D, anaphase (× 375). E, two transverse sec-
+tions of archegonium (× 375). F, section of macrospore
+and large prothallium (× 68); &c., indusium.
+
+PTERIDOPHYTA
+287
+
+the otherwise rootless Salvinia, but it is probable that such is the case, as in other respects the embryos of Salvinia and Anola are much alike. The first leaf (cotyledon) is heart-shaped in Salvinia, funnel-form in Anola, where it encloses the stem and leaves of the young plant. In both species the leaves are large about the apex of the young shoot, and as soon as the leaves develop the characteristic cavities, the Anabena takes possession.
+
+**Family 2. Marsiliaceae**
+
+The Marsiliaceae also contain two genera, which are evidently related to each other, and differ less, so far as the sporophyte is con-
+![]()
+A: A flower with five petals.
+B: A spore-carp (× 3).
+C: A spore-carp of Marilia vestita × 3.
+D: Germination of spore-carp, the meri., s., attached to a gelatinous ring (× 3).
+
+
+cerned, from the ordinary Ferns than do the Salvininaceae. The two genera, Marilia and Philularia, are usually amphibious in habit, growing in the water during their early stages, but, at least in our species, ripening their spores after the water has subsided. The California species probably belong to Marilia, but they are not found by us in this country; in *Marilia vestita* there are found bulbs, which probably survive the dry season, and thus make the plant perennial. The slender creeping stem, and the position and coiled vernation of the young leaves,
+
+Fig. 92. — *Marilia vestita*. A. fruiting sporophyte (natural size). B. sporocarp (× 3). C. spore-carp of *Marilia vestita* × 3. D. germination of sporocarp, the meri., s., attached to a gelatinous ring (× 3).
+
+288
+BOTANY
+
+are very similar to the habit of the common Ferna. The apical growth of the stem and leaves, and their structure, are also very much like those of the true Ferna.
+
+The prostrate stem is divided into nodes, which bear the lateral organs, leaves, roots, etc., (Fig. 250). The leaves are provided with a four- divided lamina in Marsilia, but in Philariaea they are aleneder, pointed structures, without any evident lamina. In Marsilia, the lamina is traversed by numerous dichotomously branched veins. The stem is monostelic, i.e., composed of one layer of cells only. The roots are produced freely from the ventral side of the nodes, and in their structure and development are not essentially different from those of the other Ferns.
+
+The Sporocarp.
+
+The sporangia in the Marsilaeae are borne in peculiarly modified leaf-segments or sporocarps (Fig. 251, B, C), which are very different from those of the true Ferns. According to Johnson (31, 22), these are marginal in origin. In Philariaea they are more centrally placed than in Marsilia, compared to the modified sporangial leaf-egmoms of Anemia, or to the sporangial leaf-egmoms of the Marilaeae. These facts show some evidence of affinity. The young sporocarp arises from a fourth-order lateral leaf-cell, and ultimately forms a globular body (Fig. 251, A), which is enclosed by a pericarp (Marsilia) body. According to Johnson, the sporangia arise from two layers of cells on either side of the Schizacranes; but they are very early ended by the excessive growth of the pericarp, which forms the young sporocarp. There are usually two sporangia in each segment of Philariaea, which is divided into four parts, perhaps corresponding to the four lobes of the Schizacranes; but they are larger in Marsilia, where the number is larger, and there are three or four, the ripe sporocarp splitting longitudinally.
+
+Macroporems and microporous occur among the leaves of both genera; but they are alike. There are usually eight sporogenous cells, all of which give rise to micro pores; but in the macroporous gametophytes as in the Schizacranes, but one spore reaches maturity at a time. The outer epidermal layer is made up of unicellular elements. The outer epidermal layers, as well as the sporangium-wall, and the tissues of the Schizacranes are soft and elastic when water is applied. The wall of the sporocarp is composed in Philariaea (Fig. 257) of three layers of cells, of which the middle one is extremely hard. If
+
+PTERIDOPHYTA
+289
+
+![]() A: A longitudinal section of ripe macrospore (× 60). B: nucleus. C: transverse section of the same (× 300). D, E: transverse sections. F: neck canal-cell; G: central canal-cell.
+Fig. 254. - *Marilia sessilis*. Germination of the macrospore.
+
+![]() A: A longitudinal section of young sporophyte still enclosed in the calyptrae. B: section of young sporophyte still enclosed in the calyptrae. ar, root; cot, cotyledon; st., stem-axus; sp, macrospore (× 75). C, root, r, and stem-axus, st., of the same (× 215).
+Fig. 255. *Ptilaria globifera*.
+
+200
+BOTANY
+
+this is cut through, so as to expose the inner mucilaginous tissue, and the sporocarp is placed in water, the swelling mucilage forces open the sporophore and sets free the enclosed spores. The glutinous mass has no definite shape in Pilularia, but in Marsilia it forms a thick ring, to which the spore is attached (Fig. 352, D).
+
+The Gametophyte
+
+The gametophyte of the Marsiliaceae is extremely reduced, and its development may occupy but a few hours. Thus, in *Marsilia vestita*,
+
+
+![]() A vertical section of stem apex (× 80): L. leaf; r. root; B. young leaf × 450; C. young leaf (× 450); D. older leaf; E. cross-section of young stem (× 80); x, apical cell.
+
+Fig. 352. *Marsilia vestita*. A, vertical section of stem apex (× 80): L., leaf; r., root; B., young leaf × 450; C., young leaf (× 450). D., older leaf; E., cross-section of young stem (× 80); x., apical cell.
+
+the whole development of the gametophyte, under ordinary conditions, is completed within about fifteen to twenty hours from the time germination begins. Pilularia, in which the gametophyte is not quite so much reduced, takes about two hours.
+
+*Main Gametophyte.*
+
+The main gametophyte, after cut off from a small sterile cell, which may divide again (Fig. 353). From the upper, or antheridial, cell, a single large antheridium, with two groups of sixteen sperms, is formed. In this way two antheridia are produced to represent two antherids. The sterile cells and the wall-cells of the antheridium contain numerous starch-granules, which are also found abundantly in the
+
+PTERIDOPHYTA
+291
+
+macrogamete. The spermatangia are ovoid, the cells being numerous in Mar-
+silla, where all but the lower larger cells have been shown to be derived from the
+blepharoplast. The uppermost cell has no cilia.
+
+Ferns (Gymnospermae) (Fig. 354) has the nucleus lying at the upper pole, surrounded by cytoplasm, which is free from the large starch-
+grains found in the body of the spore. In Marsella, the nucleus lies in a pro-
+tuberance on the upper side of the spore.
+
+The first division in the spore usually, but not always, separates this papilla
+from the body of the spore, whose nucleus undergoes no further divisions. The
+
+![]() B.
+![]() A.
+
+![]() Fig. 351.--Ptilota aurea. A cross-section of young sporangium, showing four
+sets of b. vascular bundles (x 80). B. wall of ripe sporangium (x 200).
+upper cell rapidly divides, and the single archegonium is soon complete. It has
+a very short neck, and the neck canal-cell does not divide further, but otherwise
+it is like the typical Fern archegonium. The spermatangia collect in great
+numbers around the base of the archegonium, apparently choking the funnel-
+shaped space in the miculae above the open archegonium.
+
+In case fertilization is prevented, the protalial tissue may continue to grow
+for some time after the ripe sporangium has been shed, and germinate in
+the absence of light.
+
+It has recently been shown that occasionally the embryo may develop without
+fertilization--one of the very few certain cases of parthenogenesis in the higher
+plants.
+
+293
+BOTANY
+
+The Embryo
+
+The first division in the embryo of Marilia is completed within about one hour after fertilization. The development of the egg and the development of the organs correspond in all respects with that of the typical Ferns. The cotyledon has no lamina, this being developed gradually in Marilia, but remaining undeveloped in Philaria.
+
+Distribution and Affinities of Mariliaeaceae
+
+Pilularia is represented in the United States by a single species, *P. Americana*, which closely resembles the European *P. globulifera*. It is not uncommon in various parts of California. Marilia is represented within our territory by a number of species, of which
+
+![]() A and B illustrations showing different stages of Pilularia development.
+
+Fig. 288. — *Equisetum telmateia*. A, female; B, male, gametophyte (× 70).
+
+*M. vestita* is the best known. *M. quadrifolia*, which occurs in a number of localities in the Eastern states, may have been introduced from Europe.
+
+The gametophyte of Pilularia is less reduced than that of Marilia, but the sporophyte of the latter is probably more like that of the true Ferns. Of these, probably the Schizaseae are the nearest existing relatives of the Mariliaeaceae.
+
+Class II. Equisetales
+
+The second class of Pteridophytes, the Equisetales, is at present represented by a single genus, Equisetum, with twenty-four species, of which fourteen occur within the United States. The habit of
+
+PTERIDOPHYTA
+266
+
+the sporophyte is most characteristic, the hollow, jointed shoots and rudimentary leaves presenting a marked contrast to the Ferns. The sporophylls are always arranged in a cone at the apex of the shoot, and the globular green spores, which germinate at once, are pro-
+vided with hygroscopic appendages, or elaters.
+
+The Gametophyte
+
+The germination of the spores begins within a few hours, and within twenty-
+four hours the root-hair is cut off from the larger protodermal cell. The latter shows
+more or less irregularity in its development, and the gametophyte shows more
+variable forms than the sporophyte. In some cases, however, a definite apical cell is
+always, a definite apical cell can be found in the young gametophyte. The older
+
+![]()
+A: A section of antheridial meristem.
+B: A section of antheridium.
+C: Two longitudinal sections of a mature antheridium (× 300).
+D: Three transverse sections of young antheridium (× 300).
+E: An operculum cell.
+F: A section of archegonium.
+G: A section of egg.
+H: A section of archesporium.
+I: A section of archesporium.
+J: A section of archesporium.
+K: A section of archesporium.
+L: A section of archesporium.
+M: A section of archesporium.
+N: A section of archesporium.
+O: A section of archesporium.
+P: A section of archesporium.
+Q: A section of archesporium.
+R: A section of archesporium.
+S: A section of archesporium.
+T: A section of archesporium.
+U: A section of archesporium.
+V: A section of archesporium.
+W: A section of archesporium.
+X: A section of archesporium.
+Y: A section of archesporium.
+Z: A section of archesporium.
+AA: A section of archesporium.
+BB: A section of archesporium.
+CC: A section of archesporium.
+DD: A section of archesporium.
+EE: A section of archesporium.
+FF: A section of archesporium.
+GG: A section of archesporium.
+HH: A section of archesporium.
+II: A section of archesporium.
+JJ: A section of archesporium.
+KK: A section of archesporium.
+LL: A section of archesporium.
+MM: A section of archesporium.
+NN: A section of archesporium.
+OO: A section of archesporium.
+PP: A section of archesporium.
+QQ: A section of archesporium.
+RR: A section of archesporium.
+SS: A section of archesporium.
+TT: A section of archesporium.
+UU: A section of archesporium.
+VV: A section of archesporium.
+WW: A section of archesporium.
+XX: A section of archesporium.
+YY: A section of archesporium.
+ZZ: A section of archesporium.
+AAAAA: An operculum cell.
+BBBBB: An operculum cell.
+CCCCC: An operculum cell.
+DDDDD: An operculum cell.
+EEEEEE: An operculum cell.
+FFFFFFF: An operculum cell.
+GGGGGGG: An operculum cell.
+HHHHHHH: An operculum cell.
+IIIIIII: An operculum cell.
+JJJJJJJ: An operculum cell.
+KKKKKKK: An operculum cell.
+LLLLLLL: An operculum cell.
+MMMMMM: An operculum cell.
+NNNNNNN: An operculum cell.
+OOOOOOO: An operculum cell.
+PPPPPPP: An operculum cell.
+QQQQQQQ: An operculum cell.
+RRRRRRR: An operculum cell.
+SSSSSSS: An operculum cell.
+TTTTTTT: An operculum cell.
+UUUUUUU: An operculum cell.
+VVVVVWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW
+XXXXXXXYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY
+ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
+
+
+gametophyte (Fig. 265) is an irregularly branched, green plant, not unlike the gametophytes in other plants. It is usually about one millimeter in length when fully grown. It generally shows an axial, finy body, with numerous irregular leaf-like lateral lobes. There is an apical meristem, which gives rise to several short lateral branches. The gametophyte is usually smaller than the sporophyte, plants being generally smaller and more irregular in shape than the female.
+
+The sex of the protoderm is largely a matter of nutrition, the better nourished cells being male. The female gametophytes are often produced by means of a
+prothallus which has already developed archegonia can, by insufficient feeding,
+be forced to develop into a female gametophyte.
+
+Antheridium. The antheridia are first formed within a month or six weeks after the spores are sown. They develop either upon the lateral branches or they may (as in Fig. 267) arise from the axils between two lateral branches. In this way as the archegonia are. In their development they correspond very closely to those of the Marattiaea, and, like the latter, they may be present a trian-
+gular opercular eck. In the development of the large, multiciliate spermato-
+
+284
+BOTANY
+
+noids, the presence of a blepharoplast, from which the cilia are derived, has been demonstrated.
+
+Archegonium. — The archegonium is formed upon the lower side of the apical meristem, much as in the Ferns ; but each archegonium is formed in connection with a lobed cell, which is situated between two adjacent cells of the same kind, and grows for some time from an apical cell. The young archegonium appears near the base of this, and is pushed over to the upper side of the prothallus by the growth of the adjacent tissue. Each archegonium thus lies between two lobes,
+
+![]() A diagram showing a cross-section of an archegonium.
+
+![]() B. A diagram showing a cross-section of an archegonium.
+
+![]() C. A diagram showing a cross-section of an archegonium.
+
+![]() D. A diagram showing a cross-section of an archegonium.
+
+![]() E. A diagram showing a cross-section of an archegonium.
+
+Fig. 300.—Equisetum saccatum. Archegonium. $d$. section of nearly ripe arche-
+gonium, with two neck canal-cells. $R$. section of open archegonium ($\times$ 250).
+$C$, $D$, two cross-sections of a young archegonium ($\times$ 500) ; $L$, lobe.
+Its own and that of the next younger archegonium. In its structure it closely
+resembles that of the ferns (Fig. 297). However, we notice, and find
+it opens these canal outward. There are usually no distinct neck canal-cells.
+
+The Embryo
+
+As in the euphorangiaceae Form, the primary, or basal, wall of the embryo (Fig.
+361) is transverse. The next divisions, which are somewhat oblique, divide the
+stem and first leaf in the upper (epiphyllic) part, while in the hypophyll half the
+root is separated from the foot.
+
+The larger of the two epiphyllic cells becomes at once the apical cell of the
+
+PTERIDOPHYTTA 295
+
+shoot. From it are soon cut off two lateral segments, which with the primary leaf-segment give rise to the first whorl of three leaves surrounding the base of the young shoot. From this time on the apical cell of the young shoot grows in the same way as that of the shoots in the mature sporophyte. The root behaves like that of the young shoot, but differs from it in being more or less cylindrical, and gametophytic, and enters the earth. The young sporophyte is thus completely surrounded by a protective sheath, which is formed by the young shoot. According to Jeffrey (30), the root to E. scolopendrium seems to arise from the epiphysis half of the embryo, but this is not certain.
+
+The growth of the young shoot is limited. After it has formed about a dozen whorls of leaves, which are almost always in threes, its growth stops, and
+
+![]() A B C D E
+
+Fig. 96. — *Equisetum scolopendrium.* Development of embryo. A, venter of recently fertilized archegonium (× 300). B, young embryo. C, D, two cross-sections of a young embryo. E, longitudinal section of an older one. r, root; st., stem.
+
+The place is taken by a lateral shoot, which develops from a bud placed at the base of the old shoot, and grows up to a second whorl of leaves. This second shoot, which grows to be somewhat larger than the primary one, and usually has four-lobed leaves instead of three, is soon replaced by a tertiary shoot formed from a basal bud in the same manner as before. This tertiary shoot is soon replaced by a fourth shoot, when finally a bud is formed at the base of one of them, which grows horizontally into the earth, and forms the rhizome, or underground stem, found in the older sporophyte.
+
+THE MATURE SPOROPHYTE
+
+The rhizome, or underground stem, found in all species of *Equisetum*, shows the same division into nodes and internodes which is found in the primary shoot. Surrounding the nodes are the leaf-
+
+206
+BOTANY
+
+sheaths, in whose axils are formed buds, which may later develop into aerial shoots, or may remain undeveloped and give rise to the roots. Not infrequently some of the buds develop into thickened tubers, which are often very large (Fig. 261). The rhizome is a long branch (Fig. 262). A section of an internode of the rhizome shows a large central cavity, and a circle of smaller ones corresponding to the fur-
+rows upon the surface of the internode. Alternating with these are
+the small vacuole bundles.
+
+Some of the buds at the nodes develop into the aerial shoots.
+These may be all alike - e.g. *E. robustum*, *E. bicolor* ; or there may be sporous sporogenous shoots, as in *E. echinata* (Fig. 263), which are followed by aerial shoots. The sporogenous shoots, in such cases, die as soon as the spores are scattered.
+
+The internodes are strongly furrowed, and the nodes concealed by
+the whole of rutilating leaves, which form the characteristic toothed sheaths. The number of leaves in a whorl ranges from three in *E. sciroideus* to forty or more in some of the larger species. The leaves are usually entirely destitute of chlorophyll, and are exten-
+sively protective in function. In *E. echinata* this range varies from about twenty to thirty centimetres (*E. sciroideus*) to ten metres in *E.
+giganteum*, which has a slender stem, about two centimetres in diamete-
+r, supported by numerous nodes and traversing which it grows. The
+shoots may be quite unbranched, or where the number of leaves correspon-
+ding to the number of leaves may be formed along the internodes, as in
+the sterile sheaths of *E. leucotricha*. The epidermis in all species is character-
+ized by the presence of large amounts of oil-cells, which render the
+surface rough as in the case of *E. robustum* and *E. bicolor*. When
+aerial shoots are, as a rule, much thicker than the rhizome, and there
+is a corresponding increase in the number of leaves at the nodes, and
+in the vascular bundles and lacuna in the section.
+
+Aerial shoots arise from nodes terminated by a very
+large stomatal apical cell whose divisions are extremely regular (Fig. 251).
+The first division-wall in each segment is parallel to the lateral face of the api-
+cal cell, so that each segment is quadrilateral in shape. The cells within each
+next divide by nearly radial walls, and in cross-section each series of segments
+shows six cells arranged like the sextant of a circle. Of the two superimposed
+sets of segments one is always on the same side as the next set of inter-
+nodes. Early periclinal divisions in the young segments separate a central
+cylinder of cells from the pin, from the outside to its region. The pin becomes destroyed in the process of growth by tearing apart its walls leaving the large central cavity found in most species. The central tissue of the nodes re-
+ mains intact and is thus formed a sort of diaphragm between the cavi-
+ties of the internodes.
+
+The leaf-axilar axis are annular outgrowths of the nodes. The initial cells of
+the segment also arise regularly from each side of the young shoot.
+These initial cells grow rapidly by alternate dorsal and ventral walls, and the
+
+![]() A. upper part of fertile shoot (× 1). B. part of rhizome with lateral shoots; T. tubers. C. cross-section of an internode (× 4); L. cortex; Lumen. D. sporophyll (× 4). E. single sporophyll (× 5); sp.-sporangium.
+Fig. 303. — *Egularion telmatica*.
+
+208
+BOTANY
+
+teeth soon become very evident, and the margin of the young sheath has a scal-
+loped outline. The number of the primary teeth may be subsequently increased
+by dichotomy of the apex. Occupying the axis of each tooth is a strand of elon-
+gated cells, which is surrounded by a sheath of parenchyma. This sheath is called the
+stem, where it joins a zone of narrow cells (procambium) immediately outside
+the phloem. The procambium is the first to appear in the bundle, and its cells are large and tracheids which arise upon its inner side.
+
+All of the bundles are short, except one, and a certain amount of active tissue (cambium) has been shown to persist in E. trinitaria, and possibly to persist in some other large species, so that a limited increase in the diameter of the stem is possible.
+
+The bundles run down through the internodes and divide into two equal parts at the node. Each branch joins a similar one for the neighboring bundle,
+so that in any internode a bundle is composed of the fusion of two branches for
+
+A.
+B.
+
+Fig. 363. — *Equisetum trinitaria.* A, section of a strong vegetative bud (*x 30*); B, lateral bud. *B*, stem-axe (*x 300*).
+
+separate bundles of the internode upon it, and the bundles in succeeding inter-
+nodes alternate with each other.
+
+The structure of these vascular bundles is collateral, with the xylem inward, the
+phloem outward, like that of the Seed-plants, especially suggesting that of many
+Monocotyledons. The primary tracheids are usually completely destroyed by
+the development of secondary tracheids, but they are sometimes preserved (*Fig. 364*). A group of secondary tracheids is formed on each side of this, but the other xylem-tubes are destroyed. In part of the bundle, the phloem contains sieve-tubes not unlike those of the Ferns; in part, however, there are numerous
+thick-walled fibrous cells.
+
+(Usually only one or two vascular bundles there is present; in *E*. trinitaria a con-
+tinuous endodermis (*Fig. 364*), and in other species—e.g., *E*. *hemicarpa*—there may also be present a second inner endodermis. Less frequently each bundle has a
+complete endodermis.)
+
+The green assimilative tissue is confined to the stem, especially to the slender
+secondary branches. In the main shoot the green tissue, in transverse section,
+
+![]() A diagram showing a cross-section of a plant's stem with various parts labeled.
+
+ITERIDOPHYTA
+
+appear as a series of separate masses of cells, separated by groups of thick-walled sclerenchyma, continuous with the hypodermis. This sclerenchyma constitutes the main support of the shoot, and is especially developed in the longitudinal ridges so conspicuous upon the surface of the shoot. The green tissue lies beneath the furrows between the ridges, and communicates with them by means of slender lateral branches. In the slender lateral branches the amount of green tissue is relatively much greater.
+
+The epidermal cells are heavily incrusted with silica, which usually forms con-spicuous tubercles upon its surface. Upon the inner surface the guard cells of the peculiar stomata are seen to be surrounded by two accessory cells, which are usually sunk below the level of the other epidermal cells, and completely covered by two accessory cells of much the same form as the true guard cells.
+
+![]()
+A diagram showing the structure of a vascular bundle from a sterile shoot.
+
+
+Fig. 264. — Equisetum sylvaticum. Vascular bundle from a sterile shoot (× 75); i, i, lacuna; x, r, tannin-cell; r, remains of the primary tracheae; en, endodermis.
+
+The branches arise as axillary buds, one corresponding to each tooth of a foliar sheath. The bud originates in a special apical cell of the stem, which gradually becomes cut out the characteristic tetrahedral apical cell. At an early period, the inner surface of the leaf-sheath, above the bud, becomes grown to the surface of the stem, and the young bud is thus protected by this sheath. It grows through the base of the foliar sheath, so that it looks as if, like the roots, it arose endogenously. The buds often remain undeveloped, but may be stimulated into growth under suitable conditions. Occasionally — e.g. E. sylvaticum — the branches may give rise to secondary branchlets.
+
+309
+
+800
+BOTANY
+
+![]() A long horizontal section of a plant stem, showing young leaves, 2, and lateral bud, 3 (×200).
+
+![]() B A transverse section of a plant stem, showing the vascular bundles (×200).
+
+![]() C A transverse section of a plant stem, showing the root-cap (×200).
+
+**Fig. 355. — Eupatorium telsmatica. Longitudinal sections near the apex of a sterile shoot, showing young leaves, 2, and lateral bud, 3 (×200).**
+
+![]() A A longitudinal section of root- apex (×200); n, r, central vessel of the vascular bundle. B, C, two transverse sections through the apex. C shows the first division in the root-cap.
+
+PTERIDOPHYTA
+301
+
+The Root
+
+The roots arise from the lowest nodes of the buds, but do not usually develop properly from the lower leaves of the rhizome. The dormant roots of the aerial shoots may, however, be formed into growth under special conditions of light and moisture.
+
+The origin of the roots and their development follow very closely those of the typical Ferns (Fig. 205). The root-cap is somewhat more massive and the stratification less evident as in most Ferns. The root-bundle in A. silvestre is triradiate in form, with a single very large vessel occupying the centre. This
+
+![]()
+A. B. C.
+Sp.
+
+
+Fig. 207. — *Equisetum silvestre.* A, young sporophyte with primary sporangial cell, sp. (*× 300*). B, C, sections of young sporangium; the archesporium is shaded.
+endodermis is double, and no pericycle is developed. The secondary roots arise from the base of the primary root, and are surrounded by a sheath consisting of each xylem-mass. The endodermal cell outside of the root-rudiment also grows and divides for a time, forming a "digestive pouch" enclosing the young root.
+
+The Sporangium
+
+The sporangia are borne upon umbell-shaped sporophylls, which are arranged in close circles, forming a cone at the top of the fertile shoot, and represent as many foliar sheaths. The young sporophyll (Fig. 207) is a nearly hemispherical body, which soon assumes a matroom form. The sporangia arise
+
+303
+BOTANY
+
+along its lower margin, and sometimes a single larger cell may be seen, to which possibly may be referred all the cells of the older sporangium, but this is not always correct, as the outer sterile spore-bearing tissue is often a single cell, the former giving rise to the greater part, at least, of the sporogenous tissue. From the outer one is developed the tapetum and the outer sporangium wall.
+
+The sporangium increases rapidly in size, and forms an oblong sac, pendulous from the lower margin of the pelate sporophyll. The sporogenous cells are very numerous, and their number increases with the increase of the sporangium, and a large number of the cells become broken down without forming spores.
+
+![]() A group of sporogenous cells, just before the final division of the spores, imbedded in the nucleated protoplasm derived from the disintegration of the tapetum. A, surface view (× 500). B, section through a young spore, showing the three membranes; m, the middle lamella (× 500). C, an older spore, showing the three membranes; m, the middle lamella (× 500). D, surface view. E, section of the wall of a ripe sporangium (× 500).
+
+Fig. 308. — *Equisetum telmatea*. A, group of sporogenous cells, just before the final division of the spores, imbedded in the nucleated protoplasm derived partly from the tapetum, partly from the sterile sporogenous tissue. The sporogenous cells finally separate into four groups of four each (× 500), and then into four spores (Fig. 309). The ripe spores have the outer spore-wall split into four stripes, elaters, which are exceedingly hygroscopic, and by their pressure, as the sporangium dries out, they are forced out of their place on the spore about the globular spore, but spread out when they are dry, and by their movements probably aid in distributing them. The ripe spore contains numerous crowded chloroplasts.
+
+The sporogenous cells, before their final division, separate into small groups,
+which are surrounded by a mass of nucleated protoplasm, derived partly from
+the tapetum, partly from the sterile sporogenous tissue. The sporogenous cells finally separate into four groups of four each (× 500), and then into four spores (Fig. 309). The ripe spores have the outer spore-wall split into four stripes,
+elaters, which are exceedingly hygroscopic, and by their pressure, as the sporangium dries out, they are forced out of their place on the spore about
+the globular spore, but spread out when they are dry, and by their movements probably aid in distributing them. The ripe spore contains numerous crowded chloroplasts.
+
+PTERIDOPHYTA
+303
+
+The ripe sporangia open by a ventral cleft. The dehiscence is caused, in part, by the contraction of the cells which form its outer wall (Fig. 268). These cells develop upon their walls spiral thickening-like that of the leaves, and the increased thickness of the lamina of the elaters also contributes to the opening of the sporangium.
+
+**Classification and Distribution**
+
+The existing species of Equisetales are all referable to a single order, Equisetaceae, with one genus, Equisetum, which is represented in all parts of the world except Australia. From a study of the fossil remains, it is clear that these plants were much larger and more specialized than their living descendants. These specialized types may be referred to a well-defined order, Calamariaceae, but the best evidence indicates that this order is not distinct from the Equisetaceae in being much larger and showing a secondary thickening of the stema, now merely hinted at in such species as *E. tenuifolia*. The leaves of some of these fossils have been described under the name *Caulinaria*, and the best-known of these forms belong to the type *Calamaria*. Though fossil Equisetales have in many cases been preserved so perfectly that their internal structure is readily made out. The earliest forms appeared in the Devonian, and they reached their maximum during the Carboniferous, declined rapidly in importance in the later forms. Heterospory has been demonstrated for some of them, but it never was as well developed as in the Ferns and Lycopsidae.
+
+**Class III. LYCOPODIALES**
+
+The existing Lycopodiales, or Club-mosses, are intermediate in number of species between the Equisetales and Ferns. About 450 species have been described. The great majority are tropical, but several species of Lycopodium and Selaginella are common plants in the cooler parts of the earth.
+
+The gamophytes are known in several species of Lypopo-
+dium and Selaginella, and possibly in Pellaea, but is quite unknown in the other genera. Of special importance are the investigations of Trehb, Goebel, and Bruchmann (13) upon Lycopodium.
+
+The sporophyte of all the existing species is moderate size, never exceeds 10 cm., and is usually smaller and commonly is much smaller. It usually consists of a creeping stem, with upright, leafy shoots, but in some of the larger tropical species of Selaginella the long, half-climbing stem is supported by other plants. Many tropical forms are leafy species, as may be seen in *Pleopeltis* (Plate 1).
+
+The existing Lycopodales may be divided into three orders:
+
+![]() A diagram showing the structure of a fern spore.
+
+304
+BOTANT
+
+Lycopodiineae, Ptilotineae, Selaginellineae. The two first are homo-
+sporous, the latter heterosporous.
+
+ORDER I. LYCOPODINEAE.
+The Lycopodiineae include about one hundred species, all of which,
+except the peculiar *Phylloglossum Drummondii* of Australia, belong
+to the genus Lycopodium, which includes the common "Club-
+mosses," "Ground-pines," etc., of
+
+![]() A diagram showing the structure of a Lycopodium plant.
+
+Fig. 269. — A. *Lycopodium clavatum*, gametophyte (× 5). B. *L. annotinum*, gametophyte (× 5). C. *L. clavatum*, sporophyte (× 3). D. *L. annotinum*, sporophyte (× 3). E. *L. annotinum*, section of stem (× 3). F. *L. annotinum*, spore (× 100). G. *L. annotinum*, spore (× 100). H. *L. annotinum*, spore (× 100). I. *L. annotinum*, spore (× 100).
+
+the northern forests. Some of
+the tropical species, like *L. phleg-
+maria*, are epiphytes.
+
+![]() A diagram showing the structure of a Lycopodium plant.
+
+Fig. 270. — A. *Lycopodium clavatum*. B. *L. annotinum*. C. section of the stem of *L. annotinum*.
+
+The Gametophyte.
+Our knowledge of the gametophyte of Lycopodium is now quite complete.
+There are a number of distinct types, which ought, perhaps, to lead to a sepa-
+ration of the genera into several families, but this has not yet been done.
+*L. clavatum*—the prothallium (Fig. 271) consists of an upright cylindrical body
+terminating in a crown of green leaflike lobes, among which the sexual organs
+are found; these consist of a central male organ and two female organs on either
+side of it; the whole is attached by a stalk to the gametophytic plant, like that in Botrychium. In *L. pterogramma*, the apogamotic gametophyte grows below the bark of decaying branches. Where the germination of the spores has been studied, it has been found to arise from a similar body, the primary
+tuberule, from which the gametophyte develops as a branch.
+
+![]() A diagram showing the structure of a Lycopodium plant.
+
+PTERIDOPHYTA
+305
+
+Sexual Organs. -- The gametophyte is usually monocious. The archegonium closely resembles in structure the development that of the heterosporous
+emergonangiate Ferns. The spermatangia, however, are much smaller, and are
+biciliate like those of the Bryophytes. This fact, together with the structure of
+the archegonium, leads to the conclusion that the Pteridophyta are more closely
+related to the Bryophytes than to the Lycopsida. The archegonium usually has a large number
+of neck canal-cells, instead of the two found in most of the other Pteridophyta,
+and the neck in cross-section sometimes shows five or six rows of outer neck-
+cells.
+
+![]()
+A: A young gametophyte.
+B: A mature gametophyte.
+C: A mature gametophyte with sporophyte attached (x 12).
+D: An older one.
+E: Prothallus; E, root; F, rhizoid; G, sporangium; H, archegonium.
+
+
+Bruchmann (13), who has made the recent study of the
+gametophyte in Lycopodium, recognizes five types of gametophyte,
+all excepting the young ones being sessile. In all cases the
+chlorophyll if exposed to the light. The upright cylindrical body,
+with its crown of leaflike lobes, he compares to the radially symmetrical
+gametophyte of the Mosses, and he seems inclined to connect
+Lycoepodium with these rather than with the Hepaticae. The great
+difference in these respects between the gametophytes should be sufficient
+ground for a separation of the genus into at least two.
+
+The Embryo
+
+The embryo (Fig. 373) of Lycopodium differs from that of all other Pteridophytes except Selaginella, in having only a part of the embryo devoted to the
+formation of the sporangium. The first division in the young embryo, which
+
+X
+
+306
+BOTANY
+
+becomes very much enlarged before dividing, is transverse. The cell next the archegonium neck is the larger, and either remains undivided or divides only a few times, forming the "Suspensor." The embryo itself is developed entirely.
+
+![]()
+A. S
+B. B.
+C. C.
+D. D.
+
+
+Fig. 725. -- *Lycopodium plicatum*. Development of embryo; $S$, stem; $Cot$,
+cotyledon; $Susp$, suspensor; $R$, root. ($A$, $\times 315$; $B$, $C$, $\times 238$; $D$, $\times 175$.)
+
+(After TAYLOR.)
+
+from the lower of the two primary cells. The early divisions are like those in other Angiosperms, and a division into quadrance, and generally into octase, may usually be demonstrated.
+
+PTERIDOPHYTA
+307
+
+The development of the organs of the young sporophyte is slow, and there is a good deal of difference in this respect among the several species which have been investigated. In Lycopodium, for example, the first organ to develop is a body, the "Protocorm," which gives rise secondarily to the other organs. In the other species the embryo shows a division into two tiers, of which the lower one gives rise to the root, and the upper to the shoot (Fig. 273); the terminal one gives rise to the other organs of the embryo. A single corollary is present in L. ceramis and L. phlegmarioides, but in L. clavatum, and other species, such as L. annotinum and L. scolopendrium, they are opposite, as they are in Selaginella. In these species also, the first root to develop is that which grows downwards, and this remains long after the stem has grown, in which, moreover, the stem remains short, and numerous leaves are formed before the root develops. Where the sporophyte is developed underground, as in L. clavatum, the leaves remain small and scale-like (Fig. 269, B).
+
+![]()
+A: Longitudinal section of stem apex.
+B: Transverse section of stem apex.
+C: Apex of root.
+D: Stem.
+E: Root.
+F: Periblem.
+G: Epidermis.
+H: Root-hair initial.
+I: Calyptrogen.
+J: Leaf.
+K: Leaf base.
+L: Leaf blade.
+M: Leaf margin.
+N: Leaf sinus.
+O: Leaf base.
+P: Leaf base.
+Q: Leaf base.
+R: Leaf base.
+S: Leaf base.
+T: Leaf base.
+U: Leaf base.
+V: Leaf base.
+W: Leaf base.
+X: Leaf base.
+Y: Leaf base.
+Z: Leaf base.
+AA: Stem apex.
+BB: Stem apex.
+CC: Stem apex.
+DD: Stem apex.
+EE: Stem apex.
+FF: Stem apex.
+GG: Stem apex.
+HH: Stem apex.
+II: Stem apex.
+JJ: Stem apex.
+KK: Stem apex.
+LL: Stem apex.
+MM: Stem apex.
+NN: Stem apex.
+OO: Stem apex.
+PP: Stem apex.
+QQ: Stem apex.
+RR: Stem apex.
+SS: Stem apex.
+TT: Stem apex.
+UU: Stem apex.
+VV: Stem apex.
+WW: Stem apex.
+XX: Stem apex.
+YY: Stem apex.
+ZZ: Stem apex.
+
+Fig. 273. -- Lygodium clavatum. A, B, stem-axes (x 300). C, apex of root (x 190).
+A, C, longitudinal section; B, Cross-section. t., stem-membrane; Ph., periblem; d., epidermis; h., root-hair initial; G., calyptrogen. (After Seward.) Several endosporae are formed upon the same gametophyte, and the sporophyte remains for a very long time dependent upon the gametophyte. This and the slow development of the organs and tissues all point to the very primitive character of Lygodium.
+
+THE MATURE SPOROPHYTE
+
+In most species of Lygodium (Fig. 279) the small crowded leaves are arranged spirally about the stem, which branches freely. The branching may be either monopodial or dichotomous. In a few species --e.g. L. complanatum-- the leaves are closely imbricated, and arranged in four rows, much as they are in most species of Selaginella. The roots branch dichotomously. The leaves are always very simple in structure, with a single median vascular bundle.
+
+308
+
+308
+BOTANY
+
+Growth of the Stem.---The apex of the stem is usually a broad, much dilated cone (Fig. 275). The centre of this is occupied by a group of small initial cells, from which lateral and basal segments are cut off, apparently without any definite order. From the lateral segments are derived the epidermis and cortex; from the basal segments the vascular cylinder. The lateral branches may arise laterally, or they may be a true dichotomy of the apex.
+
+A section of the stem (Fig. 276 C) shows that the cortex is composed of a mass of cortical tissue, which in most species is composed, largely, of sclerenchyma. Bounding the central vascular cylinder is a well-defined endodermis, within which there is a layer of parenchymatous cells. The epidermis is thin and is arranged in planes which are transverse in the horizontal stems, but more or less confluent in the upright shoots, so that the system in the latter presents, in cross-section, a tracheid-like structure. In the roots, however, there is no apparent layer of phloem elements, the rest of the cylinder being occupied by parenchyma. The tracheal elements are for the most part scalariform tracheids, like those of the Ferns. The phloem-bundles are smaller, and not so well developed.
+
+![]() A - The Leaf
+The leaves are small, lanceolate, with broad bases. The leaf-margins are entire; vascular bundles is conterminate, but without definite endodermis. Where the leaves are large and show a distinct midrib occur upon both surfaces. In those species with decussate leaves, like L.
+Lycopus, a second midrib is formed upon the lower surface only.
+
+![]() B - The Root
+Like the stem, the root (Fig. 275,
+C) in Lycopus does not show a single initial cell. There are separate bundles on each side of the midrib; Calyptragenus, Derratogena, Perithem, and Pierion. The first give rise to the innermost layers of the cortex; the second to the epidermis; the third to the cortex; and the last to the central vascular cylinder. In some cases there is a true dichotomy, the initial tunic at the apical end being divided into two nearly similar groups. The structure of the tunices in the complete root is much like that of Pteris. The vascular bundle is direct.
+
+![]() C - The Sporangium
+The Sporangium (Fig. 270) is kidney-shaped appendage arising directly upon the inner surface of the sporophyll, which
+
+Fig. 274. *Lycopodium lucidulum.* A., shoot with 2 leaves; B., 2nd sporophyll; C., single gametophyte (× 4); G., growing gametophyte (× 16); L., spore (× 4). (C., after CHAMBERLAIN.)
+
+PTERIDOPHYTA
+309
+
+may be very little modified - e.g. *L. lucidulum* (Fig. 274) - or they may form cones at the ends of the shoots. In the latter case, the sporophylls have little chlorophyll, and are broader and shorter than the foliage leaves.
+
+The young sporangium consists of a group of cells near the base of the young sporophyll, which soon becomes a tetrahedral archesporium from which later the tetrahedral spores are derived. The limits of the sporangium are marked by a thickened wall. The mature ripe sporangium consists of three layers of cells, of which the innermost is the tapetum. Unlike the tapetum of the other Pteridophytes, the cells here do not become broken down. The sporangium opens by a longitudinal cleft.
+
+**Gemma**
+
+In *Lygodium selago* and *L. lucidulum*, peculiarly modified gemmae, or gemmules (Fig. 274), are often produced in large numbers. The lower leaves of these buds are thick and fleshy and protect the young stem apex until the buds are ready to grow after they are detached.
+
+**Phylloglossum**
+
+*Phylloglossum Drummondii* is a little Australian plant, apparently related to Lygodium, and having a striking resemblance to the young sporophylls of *Ceratopteris*, so that it has been thought that it may represent the primitive type of the order. Unfortunately nothing is known of the gametophyte and embryo.
+
+Order II. **Pellionaceae**
+
+This is a small order of mostly tropical plants, represented in our terri-
+![]() A diagram showing a branch with a small aerial shoot growing from its node.
+![]() B A branched aerial shoot, growing from the node of a stem.
+![]() C A branched aerial shoot, growing from the node of a stem.
+![]() D A branched aerial shoot, growing from the node of a stem.
+![]() E A branched aerial shoot, growing from the node of a stem.
+![]() F A branched aerial shoot, growing from the node of a stem.
+![]() G A branched aerial shoot, growing from the node of a stem.
+![]() H A branched aerial shoot, growing from the node of a stem.
+![]() I A branched aerial shoot, growing from the node of a stem.
+![]() J A branched aerial shoot, growing from the node of a stem.
+![]() K A branched aerial shoot, growing from the node of a stem.
+![]() L A branched aerial shoot, growing from the node of a stem.
+![]() M A branched aerial shoot, growing from the node of a stem.
+![]() N A branched aerial shoot, growing from the node of a stem.
+![]() O A branched aerial shoot, growing from the node of a stem.
+![]() P A branched aerial shoot, growing from the node of a stem.
+![]() Q A branched aerial shoot, growing from the node of a stem.
+![]() R A branched aerial shoot, growing from the node of a stem.
+![]() S A branched aerial shoot, growing from the node of a stem.
+![]() T A branched aerial shoot, growing from the node of a stem.
+![]() U A branched aerial shoot, growing from the node of a stem.
+![]() V A branched aerial shoot, growing from the node of a stem.
+![]() W A branched aerial shoot, growing from the node of a stem.
+![]() X A branched aerial shoot, growing from the node of a stem.
+![]() Y A branched aerial shoot, growing from the node of a stem.
+![]() Z A branched aerial shoot, growing from the node of a stem.
+
+Figs. 275. — *Pleurotum triradiatum*. *A.* dichotomously branched aerial shoot, growing from the rootlike base; *B.* lateral branch slightly enlarged. *C.* trilocular syngamy; with trilocular sporophyll below it. (After Bux-TRAND.)
+
+310
+BOTANY
+
+tory by *Palotum tricornutum*, which is found sparingly in Florida and the adjacent region. A second genus, Tmesipteris, occurs in the Aus-
+tralian region; they are usually epiphytes of poor habit and their affinities with this group are very doubtful. In the stem-structure they show a resemblance to the extinct class Spheno-
+phyllata, with which they may possibly be remotely related. Un-
+fortunately nothing is certainly known of the gametophyte.
+The sporophyte in *Palotum* (Fig. 275) is leafless and the roots are replaced by creeping rhizomes from which dichotomously branched shoots de-
+velop. The leaves are opposite, in groups of three, and probably take the place of a haustorial connexion,
+whether or not the whole synangium is the equivalent of a single sporangium in Lycoptodium.
+
+Ord. III.
+Selaginellineae
+The majority of the Lycoptodiales belong to this order, which includes the single large genus Selaginella, most of whose species are tropi-
+cal, although a small number occur in tem-
+perate regions. In
+Selaginella
+it differs in one very
+important particular, viz., it is markedly heterosporous. Some of
+the species have the leaves alike, and
+the stems are simple; others have separate
+stems with four rows of dorsal leaves, two large and two small—
+e.g. *S. opus*, *S. kraussiana*, etc. (Fig. 279). The creeping forms
+usually develop peculiar leafless pendent branches (Rhizophores),
+from which the dichotomous branching of the shoots is only monopodial. The sporangia are borne in the axils of slightly modified leaves
+
+![]()
+A B C D E F G
+
+
+Fig. 276.—A, B, C, three views of the young anthero-
+dium of *Selaginella* *Eraunata* (*× 400*). D, an older sporidium (*× 400*).
+E, F, G, three views of a young sporidium of *S. cupressina* (*× 1100*). (After HALLER.)
+310
+
+PTERIDOPHYTA
+311
+
+arranged in a spike. In most species, the oldest (lowest) sporangium contains four very large macrospores; the others, many small microspores.
+
+The Gametophyte
+
+Male Gametophyte. — At the time the microspores are shed, there has already been cut off from the body of the spore a small sterile cell (Fig. 275, z). The large cell now undergoes repeated divisions, resulting in a single anthidium,
+
+![]() A: A section of germinating macropore. A, with free nuclei. B, showing first cell-formation (× 300); per., spore-membrane. C: section of fully developed gametophyte, with young embryo (× 300). D: early development of antheridium (× 300). E: young embryos (× 300) s., suspensor.
+![]() F: Section of fully developed gametophyte. G: young embryo (× 300). H: young embryo (× 300). I: young embryo (× 300).
+![]() J: Young embryo (× 300).
+![]() K: Young embryo (× 300).
+![]() L: Young embryo (× 300).
+![]() M: Young embryo (× 300).
+![]() N: Young embryo (× 300).
+![]() O: Young embryo (× 300).
+![]() P: Young embryo (× 300).
+![]() Q: Young embryo (× 300).
+![]() R: Young embryo (× 300).
+![]() S: Young embryo (× 300).
+![]() T: Young embryo (× 300).
+![]() U: Young embryo (× 300).
+![]() V: Young embryo (× 300).
+![]() W: Young embryo (× 300).
+![]() X: Young embryo (× 300).
+![]() Y: Young embryo (× 300).
+![]() Z: Young embryo (× 300).
+
+Fig. 277.—Selliguella Eucosmia. Female gametophyte and embryo. A, B, sections of germinating macropore. A, with free nuclei. B, showing first cell-formation (× 300); per., spore-membrane. C, section of fully developed gametophyte, with young embryo (× 300). D, early development of antheridium (× 300). E, L, young embryos (× 300) s., suspensor.
+
+consisting of a central mass of sperm-cells, and a layer of peripheral cells, which are finally broken down. The minute spermatocysts are biciliate like those of Lycopodium.
+
+Female Gametophyte. — The macropore begins its germination while still within the sporangium, in this respect approaching the condition found in the seed-plants. The macropore is surrounded by a thin wall and a very little cytoplasm, most of its cavity being filled with transparent cell-lap. As the spore enlarges, the cytoplasm becomes more free from the wall, and the nucleus separates from the contracted cytoplasm by means of an appearance of a large nucleus with a nucleolus. As the nucleus divides, the cytoplasm
+
+312
+BOTANY
+
+![]()
+A. A macrospore with gametophyte, Pr (× 30).
+B. Young sporophyte, still attached to the spore (× 8).
+C, D, older stages (× 6).
+
+
+**Fig. 278. — Scaphiella Krenzelana.**
+
+![]()
+A. A branch with sporangial cone, sp (× 3).
+B. Section of cone; mi, macrosporangium; ma, microsporangium (× 5).
+
+
+**Fig. 279. — Scaphiella Krenzelana. Branch with sporangial cone, sp (× 3).**
+R, young rhizoids.
+B, section of cone; mi, macrosporangium; ma, microsporangium (× 5).
+
+PTERIDOPHYTTA
+815
+
+Increases in quantity, and when the spore is about half grown, a section through it shows a thin layer of protoplasmic cells, which are surrounded by numerous cell-walls (Fig. 277, A, B). This closely resembles the early stage in the development of the gamopyle among the lower seed-plants. The cell- formation is at first very rapid, but as the spore grows older, the more developed connecting filaments, forming more or less evident bundles of fibres, and between each pair of nuclei a cell-wall is developed, so that the protoplasmic layer is divided into two distinct layers. These layers are separated by a narrow space, which are followed by the formation of cell-walls, and there is then formed in the apex of the spore a flat mass of tissue, upon which the archegonia are developed. Above this flat mass of tissue, the archegonia develop, and their necks, with their gemmae, continue to develop the gamopylethys, which finally breaks open the sporomembrane, and exposes the upper part of the gamopylethys with the archegonia. The latter are small, and the neck canal-cell is uniliated.
+
+The Embryo
+
+The embryo (Fig. 277, H, I) is much like that of Lycopodium, but the first division occurs earlier than in that has increased much in size, and the suspensor is much longer. A definite apical cell is present in the stem-axon, and its daughter cells arise on either side of it. A foot is developed, and both axes become united in one of the cotyledons. The first divi-
+sion of the suspensor showed seems to be a true dichotomy.
+The elongation of the suspensor forces it down into the lower mass of tissue of the gamopylethys, and this is destroyed by pressure exerted on its growth. When it emerges from the suspensor (Fig. 278, B), it very much resembles a typical dicotyledonous seedling.
+
+THE MATURE SPORO-
+PHYTE
+
+In the creeping stem,
+the structure is mono-
+stelic, but this may be replaced in the upright shoots by a polystelic structure. The individual bundles are concentric in structure, with usually two procumbent xylem groups (Fig. 280, B). The apical growth of
+
+![]() A: A section of stem showing two vascular bundles surrounding central lumen.
+![]() B: A single bundle (x 300); x, tracheids; x', sieve-tubes.
+![]() C: Section of stem showing two vascular bundles surrounding central lumen.
+![]() D: Section of stem showing two vascular bundles surrounding central lumen.
+![]() E: Section of stem showing two vascular bundles surrounding central lumen.
+![]() F: Section of stem showing two vascular bundles surrounding central lumen.
+![]() G: Section of stem showing two vascular bundles surrounding central lumen.
+![]() H: Section of stem showing two vascular bundles surrounding central lumen.
+![]() I: Section of stem showing two vascular bundles surrounding central lumen.
+
+Fig. 280.—Selaginella kraussiana. d., section of stem, showing the two vascular bundles sur-
+rounded in the central lumen (× 70). E., a single bundle (× 300); x., tracheids; x', sieve-tubes.
+
+314
+BOTANY
+
+the shoot is variable. Usually, but not always, a single initial cell can be seen. The cortical tissue is in most species composed of delicate parenchyma, and about the vascular bundles are large air-spaces. In species of dry regions, like S. rupicola, the cortical tissue is largely sclerenchymatous.
+
+The Leaf
+
+The general structure of the leaf is like that of Lycopodium, but there is always present a peculiar structure, the ligule (Fig. 281, f). Like the stem, the leaf in most species is traversed by longitudinal air-channels. A marked peculiarity of the green tissue of Selaginella is the presence of but a single chloroplast in each cell.
+
+![]()
+A. t
+B.
+C.
+
+
+Fig. 281.--Selaginella Eramosa. Section of microsporangium (× 100): t, ligule of subtending leaf; t, tapetum. B, wall of young macrosporangium; t, tangential cells (× 600). C, membrane of young macrospore.
+
+The Root
+
+The root, like the shoot, shows a single initial cell. The apparently dichotomous branching is stated to be a false dichotomy, similar to that of the stem Apex. The vascular bundle of the root is monarch, and a distinct endodermis is not developed.
+
+The Sporangium
+
+The sporangia (Fig. 281) in the investigated species of Selaginella arise from the axis, just above the origin of the subtending leaf. In
+
+PTERIDOPHYTTA
+315
+
+their development they agree closely with Lycopodium, and as in that genus the tapetum is the innermost of the three layer cells forming the wall of the sporangium. The tapetal cells remain intact, and form an epithelial layer in contact with the developing spores, to which they doubtless furnish food in a manner analogous to that found in the corresponding cells of the ovule in the Seed-plants.
+
+Up to the separation of the individual sporogenous cells, micro-sporangium and macrosporangium develop alike; but while all the sporogenous cells in the microsporangium produce tetrams of spores, in the macrosporangium this is true only of one of them, the others remaining undivided, and finally be- ing destroyed by a developing macrosporic tetram, whose spores reach a very large size.
+
+THE ISOETACEAE.
+
+The Isoetaceae are so different from other Pteridophytes that there is much difference of opinion as to where they should be placed. Whether they are most commonly associated with Selaginella, and un- doubtfully show certain structural affinities with them, or whether they also have some points in which they seem to approach more nearly the cupressaceous plants, which they are sometimes associated with. Whether they are assigned to the Fili- cales or to the Sphenopsidae, they must be placed in a dis- tinct order. There is a single genus, Isoetes, with perhaps fifty species, of which sixteen occur within the United States.
+
+The sporophyte is very similar to all of them, and is usually aquatic, although there is a number of terrestrial and am- phibious species. The stem is very short, and completely concealed
+
+![]()
+A. A section through a sporangium showing the tapetal cells.
+B. A section through a sporangium showing the tapetal cells.
+C. A section through a sporangium showing the tapetal cells.
+D. A section through a sporangium showing the tapetal cells.
+E. A section through a sporangium showing the tapetal cells.
+F. A section through a sporangium showing the tapetal cells.
+G. A section through a sporangium showing the tapetal cells.
+H. A section through a sporangium showing the tapetal cells.
+I. A section through a sporangium showing the tapetal cells.
+J. A section through a sporangium showing the tapetal cells.
+K. A section through a sporangium showing the tapetal cells.
+L. A section through a sporangium showing the tapetal cells.
+M. A section through a sporangium showing the tapetal cells.
+N. A section through a sporangium showing the tapetal cells.
+O. A section through a sporangium showing the tapetal cells.
+P. A section through a sporangium showing the tapetal cells.
+Q. A section through a sporangium showing the tapetal cells.
+R. A section through a sporangium showing the tapetal cells.
+S. A section through a sporangium showing the tapetal cells.
+T. A section through a sporangium showing the tapetal cells.
+U. A section through a sporangium showing the tapetal cells.
+V. A section through a sporangium showing the tapetal cells.
+W. A section through a sporangium showing the tapetal cells.
+X. A section through a sporangium showing the tapetal cells.
+Y. A section through a sporangium showing the tapetal cells.
+Z. A section through a sporangium showing the tapetal cells.
+AA. A section through a sporangium showing the tapetal cells.
+BB. A section through a sporangium showing the tapetal cells.
+CC. A section through a sporangium showing the tapetal cells.
+DD. A section through a sporangium showing the tapetal cells.
+EE. A section through a sporangium showing the tapetal cells.
+FF. A section through a sporangium showing the tapetal cells.
+GG. A section through a sporangium showing the tapetal cells.
+HH. A section through a sporangium showing the tapetal cells.
+II. A section through a sporangium showing the tapetal cells.
+JJ. A section through a sporangium showing the tapetal cells.
+KK. A section through a sporangium showing the tapetal cells.
+LL. A section through a sporangium showing the tapetal cells.
+MM. A section through a sporangium showing the tapetal cells.
+NN. A section through a sporangium showing the tapetal cells.
+OO. A section through a sporangium showing the tapetal cells.
+PP. A section through a sporangium showing the tapetal cells.
+QQ. A section through a sporangium showing the tapetal cells.
+RR. A section through a sporangium showing the tapetal cells.
+SS. A section through a sporangium showing the tapetal cells.
+TT. A section through a sporangium showing the tapetal cells.
+UU. A section through a sporangium showing the tapetal cells.
+VV. A section through a sporangium showing the tapetal cells.
+WW. A section through a sporangium showing the tapetal cells.
+XX. A section through a sporangium showing the tapetal cells.
+YY. A section through a sporangium showing the tapetal cells.
+ZZ. A section through a sporangium showing the tapetal cells.
+AAAAA. A section through a sporangium showing the tapet...
+BBBBB. BBBBBB
+CCCCC
+DDDDD
+EEEEEE
+FFFFF
+GGGGG
+HHHHH
+IIIII
+JJJJJ
+KKKKK
+LLLLL
+MMMMM
+NNNNN
+OOOOO
+PPPPP
+QQQQQ
+RRRRR
+SSSSS
+TTTTT
+UUUUU
+VVVVV
+WWWWW
+XXXXX
+YYYYY
+ZZZZZ
+
+ma
+
+v
+
+
+
+**Figures**
+
+A - Isoetes bulbosus, Pteridophyta, slightly reduced; 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70...
+
+B - Isoetes bulbosus; C - Isoetes bulbosus; D - Isoetes bulbosus; E - Isoetes bulbosus; F - Isoetes bulbosus; G - Isoetes bulbosus; H - Isoetes bulbosus; I - Isoetes bulbosus; J - Isoetes bulbosus; K - Isoetes bulbosus; L - Isoetes bulbosus; M - Isoetes bulbosus; N - Isoetes bulbosus; O - Isoetes bulbosus; P - Isoetes bulbosus; Q - Isoetes bulbosus; R - Isoetes bulbosus; S - Isoetes bulbosus; T - Isoetes bulbosus; U - Isoetes bulbosus; V - Isoetes bulbosus; W - Isoetes bulbosus; X - Isoetes bulbosus; Y - Isoetes bulbosus; Z - Isoetes bulbosus;
+
+AA - Isoetes bulbosus; BB - Isoetes bulbosus; CC - Isoetes bulbosus; DD - Isoetes bulbosus; EE - Isoetes bulbosus; FF - Isoetes bulbosus; GG - Isoetes bulbosus; HH - Isoetes bulbosus; II - Isoetes bulbosus; JJ - Isoetes bulbosus; KK - Isoetes bulbosus; LL - Isoetes bulbosus; MM - Isoetes bulbosus; NN - Isoetes bulbosus; OO -Isoetes bulbosus; PP -Isoetes bulbosus; QQ -Isoetes bulbosus; RR -Isoetes bulbosus; SS -Isoetes bulbosus; TT -Isoetes bulbosus; UU -Isoetes bulbosus; VV -Isoetes bulbosus; WW -Isoetes bulbosus; XX -Isoetes bulbosus; YY -Isoetes bulbosus; ZZ -Isoetes bulbosus;
+
+AAAAA - Isoetes bulb...
+
+316
+BOTANY
+
+by the broad, overlapping leaf-bases, forming a structure like the scaly bulb of an Onion. The slender cylindrical leaf also suggests
+
+![]() A
+![]() B
+
+Fig. 283. — *Jaceta echinacea*. A, upper part of germinating macrospore, showing first cell-formation (× 300). B, section of complete gametophyte with the first archegonium, ×.
+
+the Monocotyledons. The stem is deeply divided into two or three lobes, between which the numerous, dichotomously branched roots are developed.
+
+PTERIDOPHYTTA
+317
+
+The leaves are developed in a compact spiral. Each season's growth is separated from the next by a series of sterile leaves, which are more or less rudimentary. In the mature sporophyte all of the leaves are sterile, but the young sporophyte has a single sporangium upon the inner face of its expanded base (Fig. 282, B). The sporangium is oval in outline, and sunk in a depression (Fovea), whose margin (Volum) may almost completely cover the sporangium, suggesting a structure comparable to the integument of an ovule. Above the Fovea is a small scale-like outgrowth, the stipula.
+
+![]() A diagram showing the structure of a young sporophyte.
+![]() B. A diagram showing the structure of an older sporophyte, still enclosed in the gametophyte.
+
+Fig. 284. — *Isoetes echinifera*. *A*, young embryo (*× 450*); *B*, older embryo, still enclosed in the gametophyte (*× 150*); *ar.*, archegonia.
+
+The Stem
+
+The stem is composed of a central vascular cylinder, made up largely of short tracheids. Outside of this is a layer of prismatic cells, which perhaps represent the primary cortex. This layer is continuous with the outer wall of the prismatic cells on the inner side, and to the cortex outside. A true secondary thickening thus takes place, but it is quite different from that of other plants.
+
+The Leaf
+
+The leaf is traversed by a single very simple vascular bundle, surrounding which are four large air-channels, separated at intervals by diaphragms. Where
+
+318
+BOTANY
+
+The sporophyte is entirely immersed no stomata develop, but where the leaf is exposed to the air, stomata are always present. Neither stem nor root develops a single apical cell.
+
+The Root
+
+The arrangement of the tissues at the root Apex is not unlike that found in some Spermatophytes. There may be distinguished three initials, one for the pereone, one for the inner cortex, and one for the remaining outer tissues. The vascular bundle is monarch.
+
+The Sporangium
+
+The development of the sporangium (Fig. 265) is not unlike that of Lycopodium. According to R. Wilson Smith, who has recently studied the develop-
+
+![]()
+A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
+
+
+Fig. 265. — *Inocer* echinocarpa. A, section of young sporophyll (× 250); Lignule; the sporangial cells have the nuclei shown. B, section of a portion of young macrosporangium (× 320); the sporogenic cells have the nuclei indicated. C, cross-section of young microsporangium (× 250); a, volume; r, trabeculae. (After Wilson Swain.)
+
+
+ment in *Inocer* echinocarpa, the young sporangium arises from a group of superficial cells, some of which, by periclinal divisions, give rise to an inner layer of sterile cells. All these sterile cells then divide periclinally and these sterile cell-planes form a tube or stratum (Trabecula), partially dividing the mass of fertile cells. In their early stages the macro- and microporangia are not distinguishable from each other. The division of the sporangium cannot be traced to the division of a definite hypodermal cell, as was formerly supposed to be the case. The microspores are usually of the bilateral type, the macrospores being tetradal. The number of microspores in *I. echinocarpa* is 150,000 to 300,000, of macrospores 150 to 300.
+
+PTERIDOPHYTTA
+319
+
+The Gametophyte
+
+The microspores produce an exceedingly reduced gametophyte (Fig. 283, C).
+A small sterile cell is first cut off, and the body of the spore then divides further, so that four cells are formed. These divide again, and thus eight cells are produced, broken down, result.
+The development of the female gametophyte (Fig. 283 D) is much like that of Selaginella. The egg is formed by the fusion of two nuclei, and the two polar nuclei are formed before any cell-divisions occur. The archegonia are much larger than those of Selaginella, and resemble more nearly those of the eupho-
+ragiales. The egg is surrounded by a thick albumen, which is very rare in this plant, notably the absence of a suspensor. In the origin of the stem-axes of the embryo, hoeces resembles also some of the Monocotyledons.
+
+Fossil Pteridophytes
+
+On comparing the fossil Pteridophytes with their living descendants,
+it is evident that they have undergone great changes in structure, and that
+has changed very much. During the Palaeozoic age, the Ferns were almost entirely eusporangiate types, the Marattiales being especially well represented. The Leptosporangiate do not become at all prominent until the Carboniferous period, from which time they increase rapidly in importance, until they have become the dominant type among the primitive Eusporangiate.
+
+The other two classes, Equisetales and Lycopodiales, have not succeeded in adapting themselves to modern conditions, and these classes, especially the former, are but degenerate remnants of once much more important types. The more highly specialized arborescent forms, like Calamites and Lepidodendron, have entirely disappeared. It is possible that other types that have persisted may yet survive as primitive Eusporangiate.
+
+Whether Lepidodendron may have given rise to one or more de-
+scendants is a disputed question.
+
+It is evident that some of the fossil Pteridophytes are not really assignable to any living class. This is notably the case with the Sphenophyllales, a group which in its anatomical structure seems to partake of the character of both Equisetales and Lyco-
+pdales. It is possible that the Palaeotaces may be remotely related to the mosses. It is probable that an important class of extinct plants are the Cycadeo-silice, which were intermediate in their characters between Ferns and Cycads.
+
+BIBLIOGRAPHY
+
+96. 1. Arnoldi, W. Die Entwickelung des weiblichen Vorkemts bei den heterosporen Lycoptidaeaeen. Bot. Zeit., LIV. 1806.
+
+92. 2. Aarne, H. The Study of the Biology of Ferns. London and New York, 1892.
+
+320
+BOTANY
+
+**96.** 3. Some Problems in Sporophyll-transformation. Bot. Gaz., XXII. 1901.
+
+**87.** 4. Baker, J. G. Handbook of the Fern-allies. London, 1887.
+
+**87.** 5. De Barry, A. Comparative Anatomy of Ferns and Flowering Plants. London, 1887.
+
+**98.** 6. Belzofsf, W. Die mikroskopen Prothallien der Wasserfarne. Bot. Zeit., XVI. 1868.
+
+**7.** Biermann, H. The Order and Praxil. Berlin, 1866.
+
+**8.** Boedel, L. A. On some Points in the Anatomy of the Ophioglossaceae. Ann. of Bot., XIII. 1860.
+
+**90.** 7. Bower, C. E. On the Schizomata, Gleicheniaceae, and Hymenophylaceae. Ann. of Bot., XIII. 1860.
+
+**93-96** 8. Bower, C. E. On the Morphology of Spore-producing Members. Phil. Trans. Royal Soc., London, 1865-66.
+
+**91.** 9. Bremer, G. On the Prothallium and Embryo of *Denzia simplicifolia*. Ann. of Bot., XVIII. 1869.
+
+**91.** 10. Britton, E. G., and Taylor, A. Life-history of *Solenus pusillus*. Bull. Torrey Botan Club, XXVIII. 1901.
+
+**93-98** 11. Britton, E.G., and Taylor, A. The Keimphasmen mehrerer europäischer Lycopsiden. Gotha, 1902.
+
+**146-147** 12. Carrière, J.-B., on the Development of the Mosses and Ferns. London and New York, 1906. (Contains full bibliography.)
+
+**85.** 13. Drury, C.T., On Apocoryum, etc., Gard. Chronicle, 1888.
+
+**79-80** 14. Drury, C.T., On the Leaf and Sporangium of Marcella Annulata, 1875-76.
+
+**98-00** 15. Engler and Prantl. Natürliche Pflanzenfamilien Leipzig, 1896-1900.
+
+Bischoff, G.: *Mastixaceae*, *Ophioglossaceae*.
+Dietel, L.: *Parkeriacae*, *Polypodiaceae*.
+Fritsch, E.: (*Lycopodium*).
+Sadbecke, B.: (*Phytolipidae* in general); *Cyanobacca*, *Hymenophylaceae*, *Lycopsida*, *Equisetales*.
+
+16
+Goebel, E.: *Outline*.
+
+**90.** 17. Organographie der Pflanzen. Th II., Jena, 1900.
+
+**95-96** 18. Jeffreys, J.C., on the Morphology of *Pteridium aquilinum*. Proc. Canad., Inst., V., 1904.
+
+**20-22** 19. Development, Structure, and Affinities of Some Gymno-
+sperms and Angiosperms; *Lycopodium*, V., No. 3, 1899.
+
+**98-02** 20. Johnson, D.S.: On the Leaf and Sporangium of Marcella Annulata, on the Leaf and Sporangium of *Pteridium aquilinum*.
+
+**22-23** 21. On the Leaf and Sporangium of *Pteridium aquilinum*. Bot.Gaz., XXVI.L 1906.
+
+**24-25** 22a: Long, W.H.: On Apogamy and Development of Sporangia upon the Leaf of *Pteridium aquilinum*. Bot.Gaz., XXVI.L 1906.
+
+**25-26** 23a: Preliminary statement on the Prothallium of *Ophioglossum* pen-
+dulum; *Helminthostachys Zeylanica*, and *Polypodium sp.* Proc. Royal Soc., London, LXXXVII.L 1904; *Botanical Gazette*, LXXXVII.L 1904.
+
+**24-25b:** Lynden-Bell M.: A Study of the Gametophyte of *Selaginella apus* and *S.specepsis*. Bot.Gaz., XXII.L 1901.
+
+**27:** Oschewart, W.J.V.: Uber Entstehung der karyotischen Spindel und die Entwicklung des Embryos für wiss.Botanik, XXXI.L 1897.
+
+28
+Potonié, H.: See Engler and Prantl.
+
+29
+Pritzel, E.: See Engler and Prantl.
+
+PTERIDOPHYTA
+
+30. Sadebeck, R. See Engler and Prantl.
+31. Scott, D. H. Studies in Fossil Botany. London, 1890.
+36. Stahl, E. Die Botanische Flora. Berlin, 1875.
+36. Schenk, and Schimper. London and New York, 1898.
+36. Schultze, W. Handbuch der Pflanzengeographie. Berlin, 1897.
+37. Shaw, W. R. Pteridophytae in Marsilia. Bot. Gaz., XXIV. 1897.
+38. ——— Über die Blütenpflanzen bei Onoclea und Marsilia. Ber.
+der botanischen Gesellschaft zu Berlin, 1897.
+39. ——— The Fertilization of Onoclea. Ann. of Bot., XII. 1898.
+39. Smith, J. W. The Structure and Development of the Sporophylla of the Ferns (Pteridophyta). Oxford, 1891.
+41. Solms-Laubach, H., Countess. Fossil Botany. Oxford, 1891.
+43. Strasburger, J. Die Botanische Praxis (Flora). Leipzig, 1892.
+45. Upton, L. L., and Aitken, J., editors. Britton and Brown, Illustrated Flora). New York, 1896.
+46. Van Tisheim. Traité de Botanique.
+47. Vines, S. H. Students' Text-book of Botany.
+48. Warming, E. W. Handbook of Systematic Botany.
+
+321
+
+CHAPTER X
+
+SUBKINGDOM SPERMATOPHYTTA (SEED-PLANTS)
+
+CLASS I. GYMNOSPERMIA
+
+Heterospory occurs independently in all of the classes of Pterido-
+phytes. Two types may be recognised, that in which the contents of the germinating macrospore divide at once by cell-walls, as in Mac-
+silia and Salvinia, and that in which there is a repeated division of
+the nucleus, before cell-formation begins. The latter occurs in
+Jacobsia and Selaginella, and much more nearly resembles the condi-
+tion found among the Spermatophyta, the flowering plants, also
+known as "Phanerogams."
+
+In Selaginella, the growth of the gametophyte after the macro-
+spore begins is slow, and does not reach its full size, until the time it
+is still contained within the sporangium, whose wall-cells remain active
+until the growth of the macrospore is complete, and the develop-
+ment of the latter is largely due to material conveyed to it through
+the aqueous medium. In this way, the gametophyte is able to devel-
+opment of the gametophyte and the participation of the outer
+sporangial tissue in the growth of the spore and the contained
+gametophyte, Selaginella resembles more nearly than any other
+living Pteridophytes, the condition found in the Spermatophytes, or
+Seed-plants.
+
+The Seed
+
+In the Spermatophytes, as in Selaginella, the germination of the
+macrospore begins before it is fully grown; but unlike Selaginella, the
+ripe macrospore is not expelled from the sporangium, but remains
+permanently within it, and usually, although not always, fertilization
+of the archegonium is effected while the sporangium is still attached
+to the sporophyte. After fertilization has been effected, the outer
+tissues of the sporangium become necrotic and are replaced by new tis-
+sues covering for the enclosed macrospore, within which lie the gametophyte
+and embryo-sporophyte. Sooner or later, the sporangium falls away,
+and the collective structure, the sporangium, with the enclosed gameto-
+phyte and embryo, is known as a seed. This modified sporan-
+gium is the characteristic of all Spermatophytes, but as it is
+
+32
+
+SUBKINGDOM SPERMATOPHYTTA
+
+highly probable that seeds have arisen independently in different groups of Pteridophytes, it is by no means certain that all Spermatophytes are derived from a common stock.
+
+The protection of the macrospore with the enclosed gametophyte, within which the egg is developed, is a very advantageous adaptation, as the Spermatophytes are the plants which have proceeded best in adjusting themselves to the conditions now prevailing upon the earth.
+
+**Fertilization in Spermatophytes**
+
+The position of the female gametophyte in the Spermatophytes necessitates a different method of fertilization, and in all of these the generation of the male gametophyte takes place within the pollen-tube, into which pass the male generative cells, and these are thus conveyed to the egg-cell. Among the lowest of the Seed-plants, i.e. Cycads and Ginkgo, large ciliated spermonoids are developed within the pollen-tube, and these discharge their contents into the intitute of oilia, and the pollen-tube discharges the generative nuclei directly into the egg-cell, or into a neighbouring cell (Sterniger), through which it is conveyed to the egg. In case the pollen-tube has to traverse a thick wall, as in Coniferous Plants, it grows through them very much as the hypha of a Fungus would grow, body-bodily growing at the expense of the cells among which it passes.
+
+**The Flower**
+
+The sporophylls of the Spermatophytes are usually aggregated, and form a flower of these plants, which are often, therefore called the Flowering-plants. The flowers are not always so; however, that the cone of sporophylla in Equisetum or Selaginella might, with equal propriety, be considered a flower, and it is the seed and pollen-tube, and not the flower, which must be considered the distinctive features of this group.
+
+**The Spores**
+
+*Microspore.*—The microspores of the Spermatophytes, or pollen-spores, as they are sometimes called, are produced by meiosis from spores of the Archeogoniatæ. They always arise from the division of a sporogenous cell into four spores, and these in their structure agree exactly with those of the typical Archeogoniatæ. Like them, they are liberated from the sporangium, and complete their germination away from it.
+
+*Macrospore.*—The macrospores agree in their early development with those of the Pteridophytes, but a true tetrad division is usually absent, and only in rare cases does the spore develop an outer thick-
+
+![]() A diagram showing a flower-like structure composed of sporophylls.
+
+324
+BOTANY
+
+![]() A diagram showing the structure of a sporangium with a single macrospore enclosed by two envelopes.
+
+A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
+
+The Gametophyte
+
+Male Gametophyte. The male gametophyte is always extremely reduced. There are from one to three sterile cells, and a small anthocarpic cell (Fig. 267, C, D) within which is a nucleus, which usually divides into two, the male or generative nuclei. These correspond to the spermoducles of
+
+![]() A diagram showing the structure of a sporangium with a single macrospore enclosed by two envelopes.
+
+Figs. 286. -- *Pinus Virginiana.* A, sec-
+tion of branch with male flowers; B, branch
+with two antheridia, or, p, pollen grains sending pollen-tube through the antheridium; C, section of ripe seed (*x 2*); p, macrospore enclosed by one or two envelopes, or integuments, which are characteristic of the ovule in all typical Spermo-
+phytes.
+
+Figs. 287. -- *Corylus americana.* A, branch with male flowers, slightly enlarged; B, male with pollen-sac (microsporangium), *x* from within; II, from without (*x* 4); C, female flower (*x* 4); D, female flower with enclosing pollen-sac; E, female flower (*x* 2). F, a scale with three ovules, o, more enlarged.
+
+Figs. 288. -- *Corydalis japonica.* A, branch with male flowers, slightly enlarged; B, male with pollen-sac (microsporangium), *x* from within; II, from without (*x* 4); C, female flower (*x* 4); D, female flower with enclosing pollen-sac; E, female flower (*x* 2). F, a scale with three ovules, o, more enlarged.
+
+SUBKINGDOM SPERMATOPHYTA
+
+326
+
+the Pteridophytes, and in exceptional cases — e.g. Cycas, Zamia— large ciliated spermatoids develop from them. The pollen-spore, when ripe, often has the antheridial cell separated from the sterile cell, and when it germinates, which it will readily do in a 10 to 15 per cent solution of sodium carbonate, the gametophyte develops through a rupture in the outer sporangium. The division of the generative nucleus commonly takes place within the pollen-tube.
+
+**Female Gametophyte** — Among the lower Spermatophytes the female gametophyte is usually a simple structure, but in the higher Spermatophytes, especially Isoetes and Selaginella. Archeogonia of the same type are developed, and the gametophyte resembles much more that of the Pteridophytes than that of the higher Spermatophytes. In the latter, however, the female gametophyte is reduced to a mere homologue of the structures found in the fully-developed macrospore, or embryo-sac, are not entirely clear.
+
+**The Embryo**
+
+Usually, each fertilized egg-cell gives rise to a single embryo, either by division or by fission after several free nuclei have been formed. In some Coniferae, how- ever, each egg gives rise to four embryo-cells (see below), as does also to that in the embryo of the Lycopodiales, is found in most Spermatophytes.
+
+**Classification of Spermatophytes**
+
+Two classes of Spermatophytes are recognized, Gymnosperms and Angiosperms, whether these are directly related may be ques- tioned. In the former the ovules, or macrosporangia, are exposed upon open sporophylls, as they are in the Pteridophytes; in the Angiosperms the ovules are always borne in a closed cavity, the ovary, and enclosed by the base of the sporophyll (sporophyll) and by the coherent bases of two or more carpels. A more important dis- tinction is the very much reduced female gametophyte of the Angiosperms.
+
+**Class I. GYMNOSPERMIA**
+
+The Gymnosperms are the oldest types of seed-bearing plants, and in many respects, especially in the character of the gametophyte,
+
+![]()
+A diagram showing a cross-section of a plant with a focus on its reproductive structures.
+
+
+**ph**
+**x**
+**p**
+**m**
+**oam**
+
+Fig. 388.—Tazettus distichus. Transverse section through a young leaf at anthesis showing (a) epidermis; (b) mesophyll; (c) vascular bundles; (d) stomata; (e) phloem; (f) xylem; (g) cambium; (h) pith; (i) endosperm; (j) cotyledon; (k) mesocarp; (l) endosperm; (m) cotyledon; (n) mesocarp; (o) endosperm; (p) cotyledon; (q) mesocarp; (r) endosperm; (s) cotyledon; (t) mesocarp; (u) endosperm; (v) cotyledon; (w) mesocarp; (x) endosperm; (y) cotyledon; (z) mesocarp.
+
+
+325
+BOTANY
+
+are more nearly related to the Pteridophytes than they are to the Angiosperma. The recent discovery of spermatozooids in several of the lower forms has emphasized the near relation of the Gymno-
+sperms to the Lycopsida, and it is probable that the latter should be included. In number, the Gymnosperms are very much inferior to the more recent and specialized Angiosperma. They nevertheless include some of the largest and most important of all plants. The prevailing form of Gymnosperm is the cone-bearing tree, well developed upon the Pacific slope of North America. The Cycadae are mostly tropical forms, much inferior in size and numbers to the Coni-
+fers. The Gaetales comprise a small number of plants of doubtful affinities.
+
+![]() A young leaf from a small plant, showing the incurved pinnae.
+![]() B, cross-section of the petiole (× 6); f b, vascular bundles;
+![]() C, gymnospermous cone (× 10); en, endosperm.
+![]() D, young leaf from a small plant, showing the incurved pinnae.
+![]() E, cross-section of the petiole (× 6); f b, vascular bundles;
+![]() F, gymnospermous cone (× 10); en, endosperm.
+
+Fig. 398. — A-C, Cycas revoluta. A, young leaf from a small plant, showing the incurved pinnae. B, cross-section of the petiole (× 6); f b, vascular bundles; m, mesophyll; en, endosperm. D-F, young leaf from a small plant, showing the incurved pinnae; t, tracheids. E, cross-section of the petiole of the cones of Zamiopsis integrifolia.
+
+**Classification of Gymnosperma.** — The existing Gymnosperma may be divided into four orders—Cycadales, Ginkgales, Coniferae, and Gaetales. To these may be added two extinct orders, Cycado-Bilaeae and Cordaitae.
+
+**Order I. Cycadales**
+
+The lowest of the existing seed-bearing plants, with the possible exception of Ginkgo, are the Cycadae, comprising about seventy-five species, for the most part confined to the Tropics. A single species, *Zamiopsis integrifolia*, occurs in Florida, and *Cycas revoluta* (Pl. IV) reaches beyond the northern tropic in Japan.
+
+. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
+
+![]() Cycas revoluta. The upper figure shows a female plant in flower; the lower figure the group of sporophylls more enlarged.
+PLATE IV
+
+SURBINGDOM SPERMATOPHYTA
+327
+
+The habit of the sporophyte in the Cycadae is fern-like, and one species, *Stangeria perennis*, was actually first described as a Fern.
+The large pinnate, or in Bowenia bi-pinnate, leaves spring from the summit of a trunk, which may be cylindrical and several metres in height, or is short and almost globular. The leaves may form a close crown, or be long and palma-like, and may be pinnate. In former cases — e.g. Cycas — they are formed in series, a whorl of foliose-leaves, which unfold simultaneously, alternating with a whorl of scale-leaves, the arrangement being analogous to those of certain Ferns with reticulate growth, such as *Struthiopteris* (Gymnospermae).
+Young leaves in Cycas (Fig. 280) have their veins coiled inward, very much as in the Ferns. The leaflets may have a single median vascular bundle, as in Cycas, but usually there are several veins, which either fork or, in Sinngeria, are forkling, like those in the leaves of many Ferns.
+
+**The Stem**
+
+The stem may remain unbranched, but in the large species, especially *Cycas revoluta*, many branches are frequently branched, this looking as if it were produced by dichotomy. Small adventitious buds are often found at the base of the stem, usually near the mid-bases. There is a secondary growth in thickness of the stem, but it is very slow, so that the stem increases but little after the crown of leaves has attained its full size.
+
+**Botany.** — The growth of the stem-arch is due to a group of initial cells. The stem shows a large central pith about which is arranged a circle of collaterals. The outermost collaterals are often reduced to scales; they show a slight development of secondary wood to the activity of the cambium; but a large part of the stem is composed of fundamental tissue. The cambium is situated between the cortex and the phloem. The phloem is developed in the cortex, outside the ring of bundles, and this gives rise to a second ring of wood and bast. This is repeated, resulting in alternating rings of wood
+
+![]() A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
+Fig. 290. — A, *Cycas circinalis*, sporophyll with ovules. o (× 1). B-E, *C. revoluta*. B, section of young ovule (× 1). E, sporophyll with microsporangia (pollen-sac), midrib and lateral veins (× 500); F, ovule (× 100). G, sporophyll with two macrosporangia (× 10).
+
+mi
+E an
+ma
+
+328
+BOTANY
+
+and bast. In addition to the primary ring of bundles, there may also be devel-
+oped accessory bundles, both in the pith and cortex, resulting in a very com-
+plicated arrangement of vascular tissue. The bundles are usually collateral, and in structure approach most nearly those of the supranodate ferns. The vascular bundles are composed of a central vascular strand, or medullary rays, such as are found in the stem of the Coniferales, but which are also found in Botrychium. There is developed in the outer cortex a mass of growing tissue, or Periderm.
+
+The Leaf
+
+Two vascular bundles enter each leaf, and fork several times, so that a cross-
+section of the petiole (Fig. 290, B) shows several bundles arranged in the form of an O. The leaves are simple, entire, and alternate. The petiole is usually un-
+divided (Cycas), or may divide.
+
+**Marattia-like** (Fig. 290, A). The petiole is numerous conspicuous gum and
+multicellular (m) which resemble very closely those of the Marattiales.
+
+**Vascular Bundle.** The bundles of the petiole in Cycas (Fig. 290, C) show a
+group of small vessels with large intercellular spaces between them on the large
+scaleformarach. The root of the bundle is composed of the phloem, which contains large sieve-tubes with lateral sieve-plaques, somewhat like those of the Ferns. These sieve-tubes are surrounded by parenchymatous cells, which are
+often encountered cells containing crystals. In Dicroidium constrictum bundle, also,
+are found in the petiole. The green tissue of the leaf forms a palisade-paren-
+chyma above and has a spongy mesophyll below. The stomata are on the upper face
+firmness to the leaf. The stomata, which show accessory cells about the guard-
+cells, are confined to the lower surface.
+
+The Root
+
+The primary root of the embryo (Fig. 291, E) develops into a thick tap-root,
+as it does in the Coniferales, and this root serves as secondary thickening due to
+the development of a cambium.
+
+**Suberated Root.** The secondary roots are sometimes developed, espe-
+cially in Cycas, which grow near the surface of the ground and show a dichomo-
+branching, which results in dense coral-like masses. Associated with these are always large air-spaces, and may perhaps be special organs for aeration
+of the roots. The presence of the Schizomycetes within the tissues may possibly be
+associated with the assimilation of nitrogen.
+
+The Sporangia
+
+The macrosporangia (ovules) and microsporangia (pollen-sacs) are all in
+Cycads borne upon different plants. In Cycas the macrosporangia (PL IV) are
+separate, and arranged like the foliage-leaves, which they also resemble in their
+plumose form. In other cycads two kinds of sporophylls are arranged in
+a thick cone (Fig. 290, F) upon special shoots.
+
+The microsporangia are borne upon the lower side of the sporophyll (Fig.
+290, C), and may be arranged so well like those of a Fern. In their origin and
+development they are evidently like the sporophylls of the Marattiales, even
+
+SUBKINGDOM SPERMATOPHYTTA
+329
+
+showing a rudimentary annulus like that of Angiopteris. The spores are bilat-
+eral in form, and the pollen-sac opens by a longitudinal slit.
+
+The mature sporophyte is a very small plant, with very slightly modified
+sporophylls (Fig. 290, A). The ovule consists of a central part, the nucellus,
+enclosed by two integuments, which become pulpy and thicken covered, look-
+ing like a large cherry or plum.
+
+The young ovule develops a mass of sporogenous tissue, a single cell of which,
+after pinching off, gives rise to the single macrospore or Embryo-sac.
+This develops a double wall, like the macropores of the Pteridophyta, but never escapes from the sporangium.
+
+The Gametophyte
+
+The microspore, before it escapes from the pollen-sac, has already divided into three cells (Fig. 290, E), one of which is much larger than the others. Of
+the two smaller ones one becomes the antheridial cell, and is carried
+into the pollen-tube when the spore
+emerges.
+
+The development of the female gametophyte is similar to that of the male gametophyte, except that it is
+like that of lichens. The primary
+nucleus of the macropore divides into a large nucleus and a smaller one,
+between which the primary cell-walls arise simultaneously. Finally the spore becomes surrounded by a peri-
+thallial tineae, and several archegonia are developed. Each archegonium
+have each a very large egg-cell, from
+which a canal-cell is later cut off.
+Two neck-cells are developed.
+
+Fertilization
+
+The fertilization (Fig. 291) has
+been recently studied in Zamia inte-
+grifolia and Cycas revoluta. At the
+apex of the pollen-tube there is formed
+a cavity, the pollen-chamber, into
+which the pollen falls, and begins its
+germination. The pollen-sac bursts
+into the tissues of the nucellus, from
+which a fluid is discharged into the en-
+vironment. The upper end, to which the
+membrane of the pollen-sac is still
+attached, immediately contracts and becomes disintegrated with the watery
+fluid within. Shortly before fertilization is to take place the nucleus of
+the antheridal cell divides, and two very large spermatids are produced,
+each provided with a spermatozoidal head. These enter into the pollen-tube then burst, and discharges the fluid contents,
+together with the spermatids, into the chamber above the archegonia, into
+which the spermatids then enter as do they in the Ferns.
+
+![]()
+A: A young sporophyte showing a rudimentary annulus like that of Angiopteris.
+B: The mature sporophyte with sporophylls.
+C: The ovule consisting of a central part (nucellus) enclosed by two integuments.
+D: The microspore dividing into three cells (one larger than the others).
+E: One of the two smaller cells becoming an antheridial cell.
+F: The antheridial cell carrying into the pollen-tube when the spore emerges.
+G: The development of the female gametophyte similar to that of lichens.
+H: The primary nucleus dividing into a large nucleus and a smaller one between which the primary cell-walls arise simultaneously.
+I: The spore becoming surrounded by a perithallial tineae.
+J: Several archegonia developed.
+K: Each archegonium having a very large egg-cell from which a canal-cell is later cut off.
+L: Two neck-cells developed.
+M: The fertilization process in Zamia integrifolia and Cycas revoluta.
+N: The upper end of the pollen-tube where the membrane of the pollen-sac is still attached.
+O: The pollen-chamber formed at the apex of the pollen-tube.
+P: The pollen-sac bursting into the tissues of the nucellus.
+Q: The fluid being discharged into the environment.
+R: The upper end contracting and becoming disintegrated with the watery fluid within.
+S: The nucleus of the antheridal cell dividing into two very large spermatids each provided with a spermatozoidal head.
+T: The spermatids entering into the pollen-tube then bursting and discharging the fluid contents together with them into the chamber above the archegonia.
+U: Into which they enter as do they in the Ferns.
+V: The fertilization process in Zamia integrifolia and Cycas revoluta.
+W: The upper end of the pollen-tube where the membrane of the pollen-sac is still attached.
+X: The pollen-chamber formed at the apex of the pollen-tube.
+Y: The pollen-sac bursting into the tissues of the nucellus.
+Z: The fluid being discharged into the environment.
+AA: The upper end contracting and becoming disintegrated with the watery fluid within.
+BB: Shortly before fertilization is to take place.
+CC: The nucleus of the antheridal cell dividing into two very large spermatids each provided with a spermatozoidal head.
+DD: The spermatids entering into the pollen-tube then bursting and discharging the fluid contents together with them into the chamber above the archegonia.
+EE: Into which they enter as do they in the Ferns.
+FF: The fertilization process in Zamia integrifolia and Cycas revoluta.
+GG: The upper end of the pollen-tube where the membrane of the pollen-sac is still attached.
+HH: The pollen-chamber formed at the apex of the pollen-tube.
+II: The pollen-sac bursting into the tissues of the nucellus.
+JJ: The fluid being discharged into the environment.
+KK: The upper end contracting and becoming disintegrated with the watery fluid within.
+LL: Shortly before fertilization is to take place.
+MM: The nucleus of the antheridal cell dividing into two very large spermatids each provided with a spermatozoidal head.
+NN: The spermatids entering into the pollen-tube then bursting and discharging the fluid contents together with them into the chamber above the archegonia.
+OO: Into which they enter as do they in the Ferns.
+PP: The fertilization process in Zamia integrifolia and Cycas revoluta.
+QQ: The upper end of the pollen-tube where the membrane of the pollen-sac is still attached.
+RR: The pollen-chamber formed at the apex of the pollen-tube.
+SS: The pollen-sac bursting into the tissues of the nucellus.
+TT: The fluid being discharged into the environment.
+UU: The upper end contracting and becoming disintegrated with the watery fluid within.
+VV: Shortly before fertilization is to take place.
+WW: The nucleus of the antheridal cell dividing into two very large spermatids each provided with a spermatozoidal head.
+XX: The spermatids entering into the pollen-tube then bursting and discharging the fluid contents together with them into the chamber above the archegonia.
+YY: Into which they enter as do they in the Ferns.
+ZZ: The fertilization process in Zamia integrifolia and Cycas revoluta.
+
+Fig. 291. 4. Cynos resoluto, pollen-tube containing large antheridal cell; an nucellus has not yet divided; but two very large spermatids have been produced from pollen-bin. B-C. Zamia integrifolia. D-E. Cycas revoluta. D. Pollen-chamber; E. Spermatids; F-G. Spermatozooids (x 75). C. Upper part of sporophyte showing three germinating pollen-spores in or near chamber above archegonia; ar. after rupture below archegonia.
+
+330
+BOTANY
+
+The Embryo
+
+Within the egg-cell the nucleus of the spermatoid fuse with that of the egg.
+The nucleus thus formed gives rise to many free nuclei (Fig. 299, B), and the cell-forming in the young embryo in Cyane is much like that of the gametophyte,
+but differs in one important respect, namely, that the young embryo remains as a sac. A very long suspensor is developed, and the embryo develops by means of this suspensor, which is a large seed when it germinates,
+the first foliole-leaf arising between them (Fig. 299, C).
+
+Where fertilization is not effected, the gametophyte has been observed to continue its growth, and produce a large or even a mass of green tissue,
+a condition unknown elsewhere among the Spermatophyta.
+
+Order II. Ginkgoales
+
+The second order of the Gymnosperms includes but a single plant,
+the curious "Maidenhair-tree," *Ginkgo biloba* (Fig. 294), of China,
+but which is extensively cultivated in Japan, and to some extent in the United States. It is a large tree, which has usually been associated with the Cycads, but which differs in several important respects, especially the character of the gametophyte, which is much more like that of the Cycads.
+
+The leaves are deciduous, and in their form and disposition they are much like those of such forms as Adiantum. The trees are dioecious like the Cycads, and the structure of the ovule and ripe seed is much the same as in the Cycadaceae. The pollen-sacs are
+
+![]()
+A - A
+B - B
+C - C
+D - D
+E - E
+r - r
+b - b
+
+
+Fig. 299. -- A, Oecus revocata, upper part of anthergonium (x 80); A', central canal-cell;
+B, B', C, C-circumferential; B', fertilized egg-cell, showing an early stage in the development of the embryo (x 10); C', an older embryo (x 6). B', a still older one, showing a further stage in development (x 5). D', a young sporophyte; E', a young sporophyte; r, the large tap-root of the young sporophyte.
+(A, after Kuroiwa. B', after Tsuru.)
+
+
+SUBKINGDOM SPERMATOPHYTA
+
+borne upon small scrophylle, arranged upon slender spikes. The germination of the pollen-pores, and the development of motile sperma-tooids, is the same as that of the Cycada, and the development of the embryo is similar.
+
+The histology of the stem of the elder sporophyte, however, is more like that of the Coniferæ.
+
+Geological History of Ginkgo. — Ginkgo is, even more than the Cycada, a left-over type. Forms undoubtedly related to Ginkgo
+
+![]() Ginkgo biloba branch of a fruiting tree, reduced.
+Fig. 35. — Ginkgo biloba. Branch of a fruiting tree, reduced. (After RANLY.)
+
+occur in the later Carboniferous, and during the late Paleozoic and early Mesozoic Ages, the order was represented by numerous species.
+
+Order III. Coniferæ
+
+Much the greater number of existing Gymnospermae belong to the Coniferæ, which include the familiar "evergreen" trees of the northern forests. The spore-pods may reach gigantic dimensions and live many hundreds of years. Several species of the Pacific coast forest attain a height of over one hundred metres, with a stem-
+
+331
+
+332
+BOTANY
+
+diameter in Sequoia of ten metres or more, near the base (Pl. I, frontispiece). The leaves are always small, and often needle-like, differing very much in this respect from the other genera. In Agathis and Araucaria, the leaves are broader than in the other genera; and in both these genera they are rudimentary and replaced by flattened branches, or phylloclades.
+
+In the other genera the branches freerly, the branching being usually very symmetrical, so that the trees often assume a conical form. This is mainly due to the persistence of the apical bud, which results in a straight central axis, on which the lateral branches are regularly disposed.
+
+Fig. 294. —Ginkgo biloba. Fruit and seed.
+(Natural size.) (After BAILEY.)
+
+A tap-root is present in the young plants, but soon dies, and may persist for a long time, but is often replaced by secondary roots.
+
+Distribution.—The Coniferae are cosmopolitan, but are best developed in the temperate regions of the northern hemisphere. They reach their greatest size in the forests of Europe and the northern Pacific, both in Asia and America. The forest of our own Pacific slope is composed in great part of coniferous trees, which here reach their greatest size.
+
+The Stem
+
+The apex of the stem in the Coniferae probably never grows from a single initial cell. A group of terminal initials, much like that in the Cycadeaceae and Lymopodium, has been demonstrated in the Abietineae. In other forms, e.g. Araucaria, Ginkgo, and Sequoia, there is no such group of initials at all; but the primary tissue-systems are continuous over the apex of the shoot. The central tissue-cylinder, from which is derived the pith, can be easily followed to the apex. At first there is a single layer of parenchymatous cells; then smaller bundles arise, and the dermalisae, or primary epidermis, forms a single layer over the apex.
+
+The leaves arise as lateral outgrowths of the stem, and show much the same distribution of their young tissue. A simple leaf-trace, or vascular bundle, passes from each leaf into the stem, and the union of these leaf-traces forms the
+
+332
+
+---
+
+PLATE V
+
+Coniferous forest of Northern California along the base of Mt. Shasta, Alder conifer, to the right Pinyon pine.
+
+SUBKINGDOM SPERMATOPHYTTA
+
+333
+
+vascular bundles of the stem, very much as in Equisetum. The branching of the stem is monopodial, the buds arising in the axils of the young leaves.
+
+![]() A diagram showing the structure of a vascular bundle in a plant.
+Fig. 256. — *Sequoia sempervirens.* Section of shoot apex (× 25); l, l, leaves; fb, vascular bundles. B, apex of shoot (× 100); d, dermatogen; pb, phloem; pl, placenta.
+
+The older stem (Fig. 256) in all Coniferae shows a central pith surrounded by a ring of vascular bundles composed of the united leaf-traces. The bundles are collateral, and the woody portion, or xylem, extraordinarily developed. The
+
+![]() A diagram showing the structure of a cross-section of a stem in a Conifer.
+Fig. 256.—A, Picea Piceaefolia, cross-section of two-year-old branch. P., pith; x, wood, showing two annual rings; com, cambium; ph, phloem; r, resin-ducts in the cortex. B, P. nigraea, cross-section of the inner part of the wood (× 280). P., pith; r, primary tracheids; P., secondary tracheids; r', resin-ducts; s, modiary ray.
+
+First-formed woody elements are small spiral tracheids in contact with the pith, and the development of the wood is centripetal. The secondary xylem is made
+
+834
+BOTANY
+
+up of tracheids of very characteristic form, arranged in radiating series. These tracheids (Fig. 297, A) are usually more or less characterized by bordered pits (Fig. 297, A), which are usually nearly round in outline but may be elongated, like those of the Cyradæ and Ferra. These pits are developed upon opposite sides of the cell wall, and are separated from each other by a space filled with the thin membrane forming the original division-wall between the young tracheid (Fig. 297, B). At intervals the tracheids are replaced by radially ex-
+tended rays of parenchymatous cells (m). These rays are formed by rings of cells, which are usually perminnystomous, but may be composed in part of horizontal tracheids.
+
+A
+B
+C
+
+![]() A radial longitudinal section of the wood, showing bordered pits upon the walls of the tracheids; m, medullary ray; P., paren-
+chyma; m', parenchyma cells.
+
+Fig. 297. — A, B, Pinus nigra. A, radial longitudinal section of the wood, show-
+ing bordered pits upon the walls of the tracheids; m, medullary ray; P., pa-
+renchyma; m', parenchyma cells. B, transverse section of wood (× 200). C,
+sieve-tubes of P. nigra (× 500). (C after STRAUSSBURG.)
+
+Outside the mass of the wood is the Cambium (c.), a zone of meristematic
+cells, which divide by periclinal walls, the cells upon the inner side becoming transverse to the axis of the stem and giving rise to the primary tissues.
+The most important elements of the latter are the sieve-tubes, which have numerous lateral sieve-planes (Fig. 297, C). Elongated parenchyma cells and
+thorn cells (laticifers) also occur in the phloem, and the medullary rays are
+continued into
+
+**Bark.** — The outer or cortical part of the young stem is composed largely of
+green parenchymatous tissue, which is covered by a layer of epidermis devel-
+oped below the epidermis, and it is to the activity of this layer that the develop-
+ment of bark is due. One of this is the Phelloderm or " Cork-cambium."
+
+In both coniferous wood these layers are composed largely of parenchyma which are structurally much like the gum and mucilage ducts of the Cyradæ. The secondary wood of Coniferae, unlike that of dicotyledonous trees, is composed exclusively of tracheids.
+
+835
+
+SUBKINGDOM SPERMATOPHYTA
+335
+
+In most Conifers there are regular periods of growth, followed by a dormant period, which in northern regions falls in the winter.
+With the renewed renewal of activity in the spring, the growth of the young tracheids is resumed. The newly formed tracheids are much larger in the radial diameter, and have thinner walls than the tracheids last formed in the autumn. This results in the sharp line between the rings of wood made during two successive years' growth. Under normal conditions, growing tracheids form each year, and the rings of wood constitute a very fair index of the age of the tree. It is probable that the largest of the living Sequoias are two thousand to twenty-five hundred years old.
+
+The Leaf
+
+The leaves of the Conifers may be inserted singly upon the shoot,
+as in Taxus and Tsuga (Figs. 308, 309); or they may be in clusters,
+or fascicles, as in Picea, Cedrus, and Larix. In the latter, and in the Bald-
+cypress and other trees of the Gulf states, the leaves are shed each year. In most Conifers they persist for several years.
+
+Each leaf receives a single vascular strand from the stem.
+This may remain undivided, or it may divide into two or more.
+A transverse section of the leaf of Picea (Fig. 309) shows the epidermal cells to be very thick-
+walled, and to contain a large
+sink in pit, overlying an air
+space in the mesophyll. In
+Picea, where the short leafy shoots (medial)
+are crowded together (Fig.
+310), showing many-leaved fascicles and two
+single leaves, I natural size).
+
+
+
+Fig. 309.—A. Picea Conferta, branch showing scars, A, where the short leafy shoots (medial) are crowded together; B, showing many-leaved fascicles and two single leaves, I natural size.
+
+B
+
+Each leaf receives a single vascular strand from the stem.
+This may remain undivided, or it may divide into two or more.
+A transverse section of the leaf of Picea (Fig. 309) shows the epidermal cells to be very thick-
+walled, and to contain a large
+sink in pit, overlying an air
+space in the mesophyll. In
+Picea, where the short leafy shoots (medial)
+are crowded together (Fig.
+310), showing many-leaved fascicles and two
+single leaves, I natural size).
+
+336
+BOTANY
+
+Scale-leaves. -- Besides the typical foliage-leaves, scale-leaves, which are purely protective and quite destitute of chlorophyll, are of common occurrence.
+These are especially well developed in the Coniferae, where they are winter-buds, terminating each season's growth, are completely covered by the scales, which usually enclose the young flowers.
+
+Branching
+All of the Conifera branch freely, and owing to the persist-
+ence of the terminal bud, both in the axils of the lateral
+shoots, the trees are exceedingly symmetrical in form. A bud may be formed in the axil of each lateral shoot, or a pro-
+portion of these develop. In the Pines, while buds are formed in all the axils of the leaves of a shoot, in the other trees, developed just below the ter-
+minal bud, give rise to the branches, which thus are ar-
+ranged in a manner that forms concentric circles being separated by inter-
+nodes representing a season's growth. This is still more
+perfectly seen in the Picea, because in this case the terminal bud is destroyed,
+one of the lateral branches below it grows upright and takes its place.
+In a few species -- e.g. Pinae Sabinaea -- the main axis very early ceases its activity, and only one or two lateral branches grow
+occurs in some other species as they grow old. This is seen in the
+Italian Stone-pine (P. piaena), P. rigida, and other species. Adventi-
+tious buds are developed in some forms, this being especially com-
+spicious in Douglas-sempervirens.
+
+The Root
+The tap-root of the young sporophyte is usually replaced by numer-
+ous lateral roots, which often spread horizontally for a long distance.
+
+The young root shows a central pleuro-cylinder, covered with a common initial layer of cells. The primary root is cylindrical. In most forms, but in the Abietes, where the number of coty-
+ledons is more than two, the number of primary xylem-masses in the root is more than two (Fig. 307, G), although not necessarily as many as the coty-
+ledons.
+
+SUBKINGDOM SPERMATOPHYTA
+337
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+2
+
+
+![]() A branch of a Sauriaceae plant with male flowers (natural size).
+A. flower, slightly enlarged, with scales three microsporangia.
+B. flower, pollens-pore, showing the wings, c. and the antherial cell, e., highly magnified.
+C. flower, with six sporophylls, one of which is slightly enlarged.
+D. shoot with two male flowers, e., slightly enlarged.
+E. shoot with six sporophylls (× 6).
+F. shoot of Picea orientalis, with two male flowers, e., slightly enlarged.
+G. shoot with two male flowers, e., slightly enlarged.
+H. sporophyll with two sporangia (× 4).
+I. sporophyll from below with two sporangia (× 4).
+J. sporophyll from below with two sporangia (× 4).
+A cambium-ring is developed in the root, outside the ring of alternating xylom and phloem masses of the primary bundle, and a secondary increase in thickness of the stem, due to this ring.
+The Flowers
+The flower of the Co-
+nifera, except the female flower of the Taxaceae, consists of a strobilus, or cone, consisting of three leaves found in the Equisetum or Lycopodiumales. Each sporophyll bears one or more sporangia (pollen-sacs), which structurally are much like those of the Pteridophyta.
+In the Taxaceae, the cone is a modified apex of a shoot (Fig. 303).
+The male flowers (Figs.
+
+Fig. 300. — A-G. Sauriaceae branch with male flowers (natural size).
+A. flower, slightly enlarged, with three microsporangia.
+B. flower, pollens-pore, showing the wings, c. and the antherial cell, e., highly magnified.
+C. flower, with six sporophylls (× 6).
+D. shoot with two male flowers, e., slightly enlarged.
+E. shoot with six sporophylls (× 6).
+F. shoot of Picea orientalis, with two male flowers, e., slightly enlarged.
+G. shoot with two male flowers, e., slightly enlarged.
+H. sporophyll with two sporangia (× 4).
+I. sporophyll from below with two sporangia (× 4).
+J. sporophyll from below with two sporangia (× 4).
+A cambium-ring is developed in the root, outside the ring of alternating xylom and phloem masses of the primary bundle, and a secondary increase in thickness of the stem, due to this ring.
+
+Fig. 301. — A-B. Picea excelsa. A. female cone, slightly enlarged; B. a sporophyll, seen from below and showing the wings and sub-ovate ovules.
+C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z-A-B-C-D-E>Figs.
+Tubular female cone (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6). Female cone ready for shedding scales (× 6).
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubular female cones.
+
+Fig. Tubular female cones.
+Tubularfemalecones
+
+Fig.![]() A branch of a Sauriaceae plant with male flowers (natural size).
+A flower slightly enlarged; B a sporophyll from below showing the wings and sub-ovate ovules; C a seed scale; D a seed scale; E a seed scale; F a seed scale; G a seed scale; H a seed scale; I a seed scale; J a seed scale; K a seed scale; L a seed scale; M a seed scale; N a seed scale; O a seed scale; P a seed scale; Q a seed scale; R a seed scale; S a seed scale; T a seed scale; U a seed scale; V a seed scale; W a seed scale; X a seed scale; Y a seed scale; Z a seed scale;
+
+A cambium-ring is developed in the root, outside the ring of alternating xylom and phloem masses of the primary bundle, and a secondary increase in thickness of the stem, due to this ring.
+
+The Flowers
+
+The flower of the Coniferae consists of a strobilus or conecone which is transformed into the apical part of a shoot.
+The male flowers are shown in Figs.
+The flower of the Taxaceae consists of three leaves found in the Equisetum or Lycopodiumales.
+Each sporophyll bears one or more sporangia which structurally are much like those of the Pteridophyta.
+In the Taxaceae, the conecone is a modified apex of a shoot.
+The male flowers are shown in Figs.
+The flower of the Taxaceae consists of three leaves found in the Equisetum or Lycopodiumales.
+Each sporophyll bears one or more sporangia which structurally are much like those of the Pteridophyta.
+In the Taxaceae, the conecone is a modified apex of a shoot.
+The male flowers are shown in Figs.
+The flower of the Taxaceae consists of three leaves found in the Equisetum or Lycopodiumales.
+Each sporophyll bears one or more sporangia which structurally are much like those of the Pteridophyta.
+In the Taxaceae, the conecone is a modified apex of a shoot.
+The male flowers are shown in Figs.
+The flower of the Taxaceae consists of three leaves found in the Equisetum or Lycopodiumales.
+Each sporophyll bears one or more sporangia which structurally are much like those of the Pteridophyta.
+In the Taxaceae, the conecone is a modified apex of a shoot.
+The male flowers are shown in Figs.
+The flower of the Taxaceae consists of three leaves found in the Equisetum or Lycopodiumales.
+Each sporophyll bears one or more sporangia which structurally are much like those of the Pteridophyta.
+In the Taxaceae, the conecone is a modified apex of a shoot.
+The male flowers are shown in Figs.
+The flower of the Taxaceae consists of three leaves found in the Equisetum or Lycopodiumales.
+Each sporophyll bears one or more sporangia which structurally are much like those of the Pteridophyta.
+In the Taxaceae, the conecone is a modified apex of a shoot.
+The male flowers are shown in Figs.
+The flower of the Taxaceae consists of three leaves found in the Equisetum or Lycopodiumales.
+Each sporophyll bears one or more sporangia which structurally are much like those of the Pteridophyta.
+In the Taxaceae, the conecone is a modified apex of a shoot.
+The male flowers are shown in Figs.
+The flower of the Taxaceae consists of three leaves found in the Equisetum or Lycopodiumales.
+Each sporophyll bears one or more sporangia which structurally are much like those of the Pteridophyta.
+In the Taxaceae, the conecone is a modified apex of a shoot.
+The male flowers are shown in Figs.
+The flower of the Taxaceae consists of three leaves found in the Equisetum or Lycopodiumales.
+Each sporophyll bears one or more sporangia which structurally are much like those of the Pteridophyta.
+In the Taxaceae, the conecone is a modified apex of a shoot.
+The male flowers are shown in Figs.
+The flower of the Taxaceae consists of three leaves found in the Equisetum or Lycopodiumales.
+Each sporophyll bears one or more sporangia which structurally are much like those of the Pteridophyta.
+In the Taxaceae, the conecone is a modified apex of a shoot.
+The male flowers are shown in Figs.
+The flower of the Taxaceae consists of three leaves found in the Equisetum or Lycopodiumales.
+Each sporophyll bears one or more sporangia which structurally are much like those of the Pteridophyta.
+In the Taxaceae, the conecone is a modified apex of a shoot.
+The male flowers are shown in Figs.
+The flower of the Taxaceae consists of three leaves found in the Equisetum or Lycopodiumales.
+Each sporophyll bears one or more sporangia which structurally are much like those of the Pteridophyta.
+In the Taxaceae, the conecone is a modified apex of a shoot.
+The male flowers are shown in Figs.
+The flower of the Taxaceae consists of three leaves found in the Equisetum or Lycopodiumales.
+Each sporophyll bears one or more sporangia which structurally are much like those of the Pteridophyta.
+In
+
+336
+BOTANY
+
+287, 300) are similar in structure in all Conifers. The sporophylls are sometimes brightly colored, red or yellow, and may be peltate (Taxus), or scale with the upper surface smooth and lower surface.
+
+A C
+
+![]() A diagram showing the structure of a male flower of Taxus brevifolia.
+
+![]() An enlarged view of the pollen-sac of Taxus brevifolia.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged, showing the ovule.
+
+![]() A section of a shoot terminating in the young ovule, sp. (x 30). B, a slightly older one, more enlarged,
+
+SUBKINGDOM SPERMATOPHYTA
+
+seminiferous scales has been much discussed, but it is probably to be considered as an outgrowth of the sponyphyll, perhaps comparable to the placenta of the Angiospermae. In the Abietineae the seminiferous scales become very much developed, and form the hard, woody scales of the ripe cone.
+
+![]() A
+![]() B
+![]() C
+![]() D
+![]() E
+![]() F
+
+**Fig. 304. — Taxus baccata. A, section of the nucellus of a very young ovule (× 150). B, sperogenous tissue from an older ovule. C, an older stage showing young embryo-sac with numerous free nuclei. E, F, cell-formation in the young gametophyte (× 500).**
+
+The young ovule is a nearly hemispherical body, about which, at a very early stage, is developed the single integument (Fig. 305, C). The spergonous tissue may be regarded as consisting of a series of cells, each of which contains two members of rows of cells, probably derivatives of single hypodermal cells. These spergonous cells enlarge, and usually divide into two or four cells, the young macrospore being formed in one of these cells (Fig. 305, D). In Sequoia (Fig. 305) several of the embryo-sac begin to develop, although only a single one reaches maturity.
+
+**Female Gametophyte.** The primary nucleus divides repeatedly, the nuclei being arranged about the wall of the young embryo-sac (Fig. 304, D). Between
+
+340
+BOTANY
+
+these division-walls are then formed, so as to divide the peripheral protoplasm into "arcsula," which are at first open below. With the following nuclear divi-
+sions, the "arcsula" become closed, and the young embryo is enclosed by the gameto-
+phyte, or "Endoperm," as it is usually termed in the Spermatophytes.
+
+Archesporial cells may be numerous, or they may be few, and in some cases large numbers over the whole of the upper part of the gametophyte (Sequoia), or they may be much fewer in number, and restricted to the apex of the gametophyte,
+
+![]() A B C D E F G
+
+Fig. 305. — Sequoia sempervirens. A, ripe cone (natural size). B, scale from young cone, showing an ovule, o, and resin-duct, r (× 30). C, section of young scale showing two archesporial cells, a and b, each divided into two cells by a wall from an older ovule, the sporogenous cell divided. E, spongyous cell divided into four (× 275). F, young archegonium. G, young embryo (× 275). (B, E, F, G,
+after Sw.)
+
+as in Pinus. In the Cupressineae they are close together. The neck may con-
+sist of but two cells (Sequoia), or there may be several (Pinus). In Abies the
+neck-cells are in two tiers. The egg-cell is very large in the Abietines, and
+preserves a large portion of its cytoplasm. In the Pinales the egg-cell is in one layer
+of cells, some of whose nuclei pass into the egg-cell before fertilization. Usually
+a ventral canal-cell is cut off from the egg, but this is probably not the case in
+Sequoia and some Cupressineae.
+
+SUBKINGDOM SPERMATOPHYTTA
+
+Fertilization. — When the female cone is ready for pollination, the scales separate and the pollen falling upon them sifts into the spaces between them. The pollen grains are carried by the wind upon the flower bents over, which probably assists in bringing the pollen upon the apex of the ovule. The integument of the latter is often pro-
+vided with prominences, which serve to hold the pollen, and a drop of fluid, which may be water, is secreted by the integument to moisten the pollen upon the apex of the nucellus, where it begins to grow.
+
+In the Pines the development of the cones requires two years.
+Pollination is effected in the spring, and the growth of the pollen-
+tube into the tissue of the nucellus begins; but growth then stops,
+
+![]() A-D E F X
+
+Fig. 306. — A, B, Pinus rigida. A, upper part of gametophyte, with two archo-
+gena (× 30). B, lower part of fertilised egg, showing first divisions (× 15).
+C, young embryo in early stage of development (× 15). D, mature embryo;
+opment of embryo; z, apical cell; sus, suspensor. (D, E × 500; F, × 270.)
+(See also Fig. 307.)
+
+and is only resumed the following spring, during which the female
+gametophyte develops and fertilization is effected. The ovule then
+has the integument hardened, and becomes the seed.
+
+The development of the pollen-tube is very much like that of the Cycads
+(Fig. 307), but the male nuclei do not develop into spermatiacones. The pollen-
+tube passes through a series of stages before it reaches the egg-cell and dis-
+charges its contents, including all the nuclei, into the egg-cell, where one of
+the generative nuclei fuses with that of the egg and completes the fecundation.
+
+The Embryo
+
+The egg may form a single embryo (Taxus, Sequoiia), or each egg gives rise
+to a group of four embryos (Pinus, Abies). The formation of the division-walls
+
+342
+BOTANY
+
+is usually preceded by a repeated division of the nucleus (Fig. 306). The em-
+bryo is always provided with an elongated suspensor, and usually grows from a
+single apical cell (Fig. 306, C), which is later replaced by a group of initial cells.
+The cotyledons range from two to six or more.
+
+The ripe seed is provided with a hard integument, or Testa, within
+which lies the embryo surrounded by the endosperm, or prothallial
+tissue (Fig. 286, B).
+
+In Cephalotaxus (Fig. 307) the integument becomes pulpy, as it does in Cycas, and in Taxus a scale-like phyllo-
+integument, or Aril, is formed. The scales of the cone usually become hard and woody in some Cupressaceae - e.g.
+Juniperus—they become pulpy and coherent, so that the cone resembles a berry.
+
+**Germination (Fig. 307)**
+
+![]() A diagram showing the germination process of a seed.
+
+**Fig. 307.** --Phalaenopsis, germination of the seed. [A, B, x; C, x; D, x; E, median section of D, more enlarged; F, cross-section of the stem showing vascular bundles; G, similar section of the root; both enlarged.] ph
+
+The germinating seed absorbs water, and the embryo begins to enlarge,
+drawing upon the endo-
+sperm, whose cells are
+filled with starch granules,
+especially oil and albu-
+minous granules. Chloro-
+phyll may be developed while the cotyledons are still enclosed in
+the seed.
+
+The root, which is directed toward the opening in the integument
+(Micropyle), pushes out through it, and bends down into the earth.
+As the cotyledons exhaust the contents of the endosperm-cells they
+withdraw from the micropyle, which closes off. A section through
+the apex of the young seed shows the contents of the stem
+surrounded by the cotyledons. Each of the latter is traversed by a
+single vascular bundle, which bends down into the stem. This in
+section shows a circle of separate collateral bundles around the
+primary phloem. These are developed by a ring of cambium,
+developed between xylem and phloem, and also between the
+bundles, and the secondary thickening of the stem begins.
+
+343
+The root is directed toward the opening in the integument (Micropyle), pushes out through it, and bends down into the earth.
+As the cotyledons exhaust the contents of the endosperm-cells they withdraw from the micropyle, which closes off. A section through
+the apex of the young seed shows the contents of the stem surrounded by the cotyledons. Each of the latter is traversed by a single vascular bundle, which bends down into the stem. This in section shows a circle of separate collateral bundles around the primary phloem. These are developed by a ring of cambium,
+developed between xylem and phloem, and also between the bundles,
+and the secondary thickening of the stem begins.
+
+SUBKINGDOM SPERMATOPHYTA
+343
+
+**Classification of Coniferæ**
+
+The Coniferae may be divided into two suborders, Taxaceae and Pinaceae. The Taxaceae comprise a single genus, *Taxus*, characterized by not having the female flowers in cones, but the ovules developed as axial structures. These are represented in the United States by the species of *Taxus* (Yew) and *Torreya*, one species of the latter growing upon the Pacific slope, the other in the mountains of Japan (Fig. 308, F), from China and Japan, is sometimes cultivated.
+
+The largest genus of the family is Podocarpus, with 150 species whose species belong to the southern hemisphere and tropical Asia.
+
+The Pinaceae include many of the largest trees, and are important of forest trees. There are two families, Abietineae and Cupressineae, which are further subdivided into several inferior groups. Of the Abietineae the majority of the species belong to the Abietineae (Abietis, Picea, Tsuga, Pseudotsuga). The principal American genera are Pinus, Larix, Abies, Picea, Tsuga, Pseudotsuga.
+
+The subfamily Taxodiaceae includes the Sequoias of the Pacific coast, and some other genera of western North America. The Japanese Cryptomeria (Fig. 287) also belongs to this group.
+
+The Cypress family is much smaller. The American genera are Cupressus, Chamaecyparis, Libocedrus, Thuja, Juniperus. Several of these genera are known as "Cedar," although the true Cedar — *Thuja occidentalis* — belongs to the Abietineae, and does not occur in America.
+
+The Coniferae reach their greatest development upon the Pacific slope. All of the American genera occur except Taxodium. Some of them, like the two Sequoias, are confined to California, which contains a number of other species of extremely limited range, like the Monterey Cypress, *Cupressus macrocarpa* (Fig. 310, A)
+
+![]() A diagram showing parts of a cone.
+A. E. *Taxus brevifolia*; ma, fe- male flower; fr, fruit; ar, aril;
+B. C. section of ovule; m., enclosed by integument; e., egg-cell;
+C. section of ovule; m., egg-cell;
+D. C. section of ovule; m., egg-cell surrounded by aril; e., embryo.
+F. *Taxus brevifolia*. (Natural size.)
+
+Pro 288
+
+A. E. *Taxus brevifolia*: ma, fe-
+male flower; fr, fruit; ar, aril;
+B. C. section of ovule; m., en-
+closed by integument; e., egg-cell;
+C. section of ovule; m., egg-cell;
+D. C. section of ovule; m., egg-cell surrounded by aril; e., embryo.
+F. *Taxus brevifolia*. (Natural size.)
+
+344
+BOTANY
+
+(Pl. XV). Of the numerous West-coast Coniferae, the most important are the Redwood (Sequoia sempervirens), Sugar-pine (Pinus Lambertiana), Yellow-pine (P. ponderosa), Incense-cedar (Libocedrus)
+
+![]() A
+![]() B
+
+Fig. 309. — A, Puya Canadensis (× 5). B, seminal scale, with large outstending scales of Pinus ponderosa (× 1). C, cone of P. Douglasii (× 7).
+
+decurrens). Ginkgo, A. biloba (Tilia biloba), Douglas-fir (Pseudotsuga Douglasii), Sitka-spruce (Picea Sitchensis) and other species of Spruces and Firs.
+
+A
+B
+
+Order IV. Gnetaceae
+
+This order includes three genera which differ much from each other, but nevertheless show certain structural resemblances in the mode of development of the seed. They differ from the Conife-
+rea in having the flowers pro-
+vided with a perianth or calyx,
+envelopes, and are sometimes
+considered to be intermediate
+in character between the Gym-
+nosperms and Angiosperms.
+
+The secondary wood contains vessels, in which respect they resemble Angiosperms. Of the three genera, but one, Ephedra (Fig. 811), is found within our territory, several species occurring in our south-
+western States. Ephedra is a tropical genus, found both in
+the old and new worlds. We find it in a monotypic form occur-
+ring in West Africa.
+
+The species of Ephedra are shrubs with jointed branches, sug-
+gesting an Equisetum. The leaves are reduced to leaf abaxials,
+
+![]() C
+![]() D
+
+Fig. 310. — A, Cupressus macrocarpa (× 1). B, ovuliferous scale, with young seeds,
+n = 22. C, ovule of Thuja occidentalis (× 3). D, Thuja occidentalis (× 2).
+
+344
+
+SUBKINGDOM SPERMATOPHYTA
+346
+
+scales about the joints. The plants are usually dioecious. The male flower (Fig. 311, C) consists of two to eight sessile stamens at the apex of a bract, which is surrounded at the base by scalelike leaves.
+
+The female flower has a single ovule, surrounded by a membranaceous integument, which projects beyond the perianth. The ovule (Fig. 311, B) is either solitary at the end of the axis, or there may be two or three in the upper axis of a cluster of bracts, the lower bracts being sterile. In the species figured, these bracts are thin and membranaceous, but they usually become thick and pulpy.
+
+The female gametophyte in Ephedra is much like that of the Conifers, and the archegonia are well developed.
+
+After fertilization, several free cells are formed from the egg-cell, each one of which produces an embryo. The embryo, in all the Gnetales, has two cotyledons.
+
+The genus Gnetum (Fig. 311, D) comprises a number of plants which are either trees or climbers. The broad, opposite leaves are strikingly similar to those of the Coniferae, and their relationship is possibly related. The flowers (E) are borne in whorls at the ends of the shoots, usually upon different plants, and structurally are similar to those of Ephedra. According to Lotay (Coulier, 4) there is not a single integument and a double perianth, the latter becoming flaccid in the fruit.
+
+**Embryosperm.** The embryosperm shows certain resemblances to that of the lowest Angiosperms. While the basal part becomes filled with protoplasmic tissue, the nuclei of the upper portion remain free, and any one may become the egg-nucleus as long as its archegonium develops. The free nucleus resulting from the fusion of a protoplast nucleus from a pollen-cube with an egg-nucleus,
+
+![]() A: Fragment of a female flower of Ephedra trichocarpa.
+![]() B: Female flower of Ephedra trichocarpa.
+![]() C: Staminate flower of E. trichocarpa.
+![]() D: Gnetum latifolium (x 1), staminate flower.
+![]() E: Female flower of Gnetum latifolium (x 4). (C after Ecklon; E after Loury.)
+
+346
+BOTANY
+
+develop, finally, into an embryo, but this does not occur until after the seed germinates.
+
+**Histology**
+
+Except for the presence of true vessels in the secondary wood, Ephedra is much like the typical Conifer. In the climbing species of Gnetum, there is formed a second cambium ring, outside the original one, somewhat as in Cycas.
+
+**Welwitschia**
+
+Welwitschia mirabilis is an extraordinary plant, with a long tap-root terminating above the ground in a short, thick stem, which bears two enormous, persistent, strap-shaped leaves. The seedling has two cotyledons, which are followed by the single pair of strap-shaped leaves, persisting as long as the plant lives. In the axis of these leaves is a central column of tissue, from which branch terminates in a cone, composed of closely set bracts, arranged in four series. The individual flowers are borne in the axils of these bracts. The male flowers have six stamens and a rudimentary ovule; the female flower has a single ovule, much like that of Gnetum, and no trace of stamens.
+
+**Fossil Gymnosperms**
+
+Many of the existing types of Gymnosperms also occur fossil, being the oldest Seed-plants. The oldest are the Ginkgoales and Cycadales, which are met with first in the late Paleozoic formations. These plants are now all extinct. Most important of these are the Condaules, which are much the oldest seed-bearing plants, occurring abundantly in the Devonian and Carboniferous strata, where they have been preserved with marvelous perfection, even the structure of the valves and pollen-sporangia being well known. There were also trees with long leaves, which were first supposed to belong to Monocotyledons. The large pollen-spores sometimes show traces of the male gametophyte, while it was evidently better developed than in any existing Spermatophytes. The seeds were probably produced by spermatids. Fertilization was apparently effected much as in the Cycads.
+
+**Cycado-fules.** — Another remarkable group of extinct plants are the Cycado-fules, including a large number of shingle-like forms, intermediate in character between the Ferns and the true Cycads. Many of these were described as Ferns, and probably approach these more nearly than they do the Cycads — e.g. Lyginodendron. Others — e.g. Cycadoxylon, Cycadopodiad — were probably more like Cycads than Ferns.
+
+**Cycadales.** — The Cycadales were especially well developed during the Mesozoic age, when numerous types, closely related to the living
+
+SUBKINGDOM SPERMATOFYTTA
+
+genera, occurred. Besides these, a second suborder, now quite extinct, was represented by numerous species. These were the Bennettites, which were much like the existing Cycads, but had much more slender leaves.
+
+**Conifera.** Most of the Conifera appear in the later Mesozoic and early Tertiary, when certain genera, like Sequoia, Torreya, and Taxodium, which are now much restricted in their range, were very widely distributed.
+
+**Affinities of Gymnosperms**
+
+The origin of the Gymnosperms and their relation to the Angiosperms is by no means clear. The Cycads are undoubtedly related to the Ferns, but the origin of the Conifers and Gnetaceae is extremely obscure. The Conifers are supposed to have arisen from Lymopsida, perhaps like the fossil Lepidodendron, but this is by no means generally accepted. The Cordaitales have been suggested as forms intermediate between Cycadae and Coniferae, but this is open to doubt. Still more uncertain is the origin of the Gnetaceae.
+
+367
+
+1. De Bary, A. Comparative Anatomy.
+2. Bunting, N. L., and Brown, A. Illustrated Flora of the Northern United States, Vol. I. 1890.
+30. Brewer, W. H., and Watson, S. Botany of California (Geological Survey of California). 1890.
+41. Coulter, J. M., and Chamberlain, C. J. Morphology of Spermatozoids and Gametophytes (This is the most recent work on Gymnosperms, and contains a full bibliography).
+47. Chandler, W. W. Flora of Southern United States. Cambridge, Mass., 1867.
+49. Eichler, A. W. Cycadaceae, Coniferae, and Gnetaceae, in Engler and Prantl's "Organismen," 1886.
+50. Gosset. Outline.
+51. Gray, A.Mansell of Botany.
+55. Lemmon, J.G. Handbook of West-American Cone-bearers. San Francisco.
+52. Luerssen, Chr. Handbuch der ayst Botanik. Bd.II. Leipzig, 1882.
+56-58 12. Sargents, C.S. Silva of North America, X, XI, XII Boston,
+13. Strasburger, E. Botanisches Practicum.
+14 Van Tieghem, Ph., Traité de Botanique.
+15 Vines, J.C., Manual of Botany.
+16 Warming, E.W. Handbook of Systematic Botany.
+17 Watson. See Brewer.
+
+![]() A page from a botanical text book.
+
+CHAPTER XI
+
+ANGIOSPERM.A (METASPERM.E)
+
+SUBCLASS I. MONOCOTYLEDONES
+
+The second class of the Spermatophytes, the Angiosperms, not only far outnumber the Gymnosperms, but all the other plants combined. Over a hundred thousand species have been described, and many new ones are being discovered every year. The Angiosperms are especially adapted to the present conditions upon the earth, and we encounter them almost everywhere, provided the conditions permit of vegetable growth. A small number, like Zoostera and Phyllospadix, are aquatic; a large number are terrestrial. Many are fresh-water aquatics, or marsh-plants, while others are adapted to extremely arid conditions. Between these extremes are found all grades of adaptation. Many forms, especially those of the Tropics, are epiphytes, while others are saprophytes or parasites.
+
+A very important factor in the success of the Angiosperms in the struggle for existence has been their utilizing animals for distributing their seeds. This is a very recent development in plant life, and has undoubtedly led to great changes on both sides. At point of numbers, the insects bear much the same proportion to other animals that the Angiosperms do to plants; and this is in some extent at least, the case with respect to the distribution of seeds among Amphibians and insects. Such insects as butterflies and bees could not exist without the Angiosperms, upon which they depend almost exclusively for food. The peculiar peculiarity of all of these groups of insects are undoubtedly the result of their association with flowers, which in their turn owe their most striking characters—color, scent, honey, and peculiar form—to the visits of insects.
+
+The persistence of the fruits of the Angiosperms, such as the development of edible pulp or burs, are adaptations for distribution of the seeds by animals.
+
+The Angiosperms agree with the Gymnosperms in the formation of seeds, and in their fertilization by means of the pollen; but this is quite as much a matter of convenience as it necessarily imply a genetic relationship of the two classes of Spermatophytes. Just as heterozygous arose independently in several groups of Pteridophytes, so seeds were probably developed in more than one group; and this would necessarily involve the development of a pollen-tube.
+
+348
+
+ANGIOSPERMÆ
+
+as only in this way could the sperm-
+nucleus be conveyed to the egg-cell
+included in the ovule. It is there-
+fore possible that the Angiosperms
+have been derived, not from the
+Gymnosperms, but directly from
+forms more nearly related to the
+Pteridophytes.
+
+Of the Gymnosperms, the genus
+*Gnetum*, with its large, naked
+gonium is developed, approaches
+more nearly, in the character of
+the gametophyte, the condition found
+in the lower Angiosperms. As it
+is questionable whether *Gnetum*
+is really related to the other Gymno-
+sperms, this does not throw much
+light upon the relationship of Gym-
+nosperms and Angiosperms.
+
+The Flower
+
+The most characteristic struc-
+tures of the Angiosperms are the
+flowers. These, in their simplest
+form, are less complex than those of some Gymnosperms,
+but they differ from these in having
+the ovule always protected within the
+ovary, which in most cases is formed from the base of a carpel, or of several coherent carpels.
+
+The simplest flower consists of a single carpel or stamen (Fig. 312),
+or a single perianth, or floral envelope.
+From this there is an all gradation of complexity to the extraordinarily specialized flowers found in the Orchids and Com-
+positae.
+
+340
+
+Fig. 311. - *A.* *Semenia zebuha*, a hypogynous flower with all the floral leaves separate; *r.*, receptacle; *a.*, calyx; *p.*, petals; *st.*, stamens; *c.*, carpel. *B.* *H. Hestoniana purpurea*, a hypogynous flower, with symmetrical corolla and compound ovary.
+
+Fig. 312. - *A.* *Corylus avellana*. A staminate flower.
+*B.* *Pistilium*, flower, enlosed.
+*C.* section of ovary, with the style and stigma.
+*D.* *Oenothera*. The flower.
+*E.* *Oenothera*. The fruit.
+*F.* *Oenothera*. The seed.
+*G.* *Oenothera*. The embryo.
+*H.* *Oenothera*. The embryo.
+*J.* *Oenothera*. The embryo.
+*K.* *Oenothera*. The embryo.
+*L.* *Oenothera*. The embryo.
+*M.* *Oenothera*. The embryo.
+*N.* *Oenothera*. The embryo.
+*O.* *Oenothera*. The embryo.
+*P.* *Oenothera*. The embryo.
+*Q.* *Oenothera*. The embryo.
+*R.* *Oenothera*. The embryo.
+*S.* *Oenothera*. The embryo.
+*T.* *Oenothera*. The embryo.
+*U.* *Oenothera*. The embryo.
+*V.* *Oenothera*. The embryo.
+*W.* *Oenothera*. The embryo.
+*X.* *Oenothera*. The embryo.
+*Y.* *Oenothera*. The embryo.
+*Z.* *Oenothera*. The embryo.
+
+350
+BOTANY
+
+The essential parts of the flowers are, of course, the sporophylla, stamens and carpels, which, in the lower floral types, are in separate flowers, often upon different plants. Such flowers are "Dielinos." In the more specialized flowers, stamens and carpels are usually together, and the flower envelope is developed. In the typical angiospermous flower, the sporophylls are surrounded by a series of sterile leaves, the floral envelope, or Perianth. These leaves
+
+![]() Nymphaea tuberosa, showing gradation of floral leaves. (After Bailey.)
+
+are in part protective, but they may also be conspicuously colored, and so render the flowers attractive to insect visitors.
+
+The typical angiospermous flower consists of a series of floral leaves, arranged either spirally or in whorls about the apex of the shoot, or receptacle. The outermost leaves form a Receptacle. The outermost leaves, the Sepals, are usually green, and are mainly protective in function. These together constitute the Calyx. The second series, the Petals, are generally larger and
+
+ANGIOSPERM.E 384
+
+conspicuously colored, and together form the Corolla. Within the corolla are the stamens, upon which are borne the pollen-sacs. The stamens is usually differentiated into two parts (Pilkington) and Anther, which is made up of the anther-lobes, the anthers, and Collectively, the stamens form the Androecium. The innermost sporophylls, the carpels, may be separate, but more commonly they are united to form a compound Pistil. Collectively, the carpe- lars constitute the Gynae- cum. The pistil is divided into three portions, the basal Ovary, within which are borne the ovules; the intermediate Stylo, with which the Ovaries are united; and the Stigma, upon which the pol- len-spores are deposited. The stigma has usually a papillate surface, with a central depression, which serves both to hold the pollen and to induce its germination.
+
+**Development of the Flower**
+
+The development of the typi- cal flower follows closely that of a vegetative shoot. The receptacle corresponds to the growing-point of the shoot; about this are produced the various floral leaves in precisely the same way that the foliage leaves are produced on a vegetative shoot (Fig. 316). The sepals are first to develop, commonly following the stamens, then the petals not infrequently becoming evident at a later period.
+
+The ovary may arise as a continuous wall about the apex of the floral axis, or the separate carpels may be evident from the first. Usually the formation of the gynaeum stops the further growth in length of the floral axis.
+
+**The Sporangia and Gametophytes**
+
+The stamen is in most cases a true foliar organ, but exceptionally— e.g. Naias—is a direct development of an axis, and the anther
+
+![]() A B C
+car
+
+![]() D E F
+an
+
+![]() G H I J K L M N O P Q R S T U V W X Y Z
+ovary
+
+![]() P
+carpels
+
+![]() Q
+ovule
+
+![]() R
+ovule
+
+![]() S
+ovule
+
+![]() T
+ovule
+
+![]() U
+ovule
+
+![]() V
+ovule
+
+![]() W
+ovule
+
+![]() X
+ovule
+
+![]() Y
+ovule
+
+![]() Z
+ovule
+
+362
+BOTANY
+
+is the transformed stem-apex. The ovule, or macrosporangium, may also be of axial origin instead of an outgrowth of the carpel (Naiais, Pepe-
+363
+
+The microsporangium corresponds in its development with that of the higher Pteri-
+dophytes and Gymnosperms.
+In Naiais, Liliae (Fig. 317), where the asexual tissue arises from the pleuron, this is formed by a series of hypodermal cells by the formation of a series of peri-
+clinal walls which form a
+section; r, meiotic cell; s, spermatium;
+A, young flower (× about 75); A', two very young flowers; B, if the ovule, e, have just appeared; C, section of ovule showing the sporogenous tissue and the epidermis. The pollen mother-cells usually separate before the first nuclear division occurs,
+and often have very thick cell-walls. The first nuclear divi-
+![]() A diagram illustrating the development of a flower in Naiais.
+Fig. 318.—Corylus bovea-patens. Development of the flower (× about 75). A, two very young flowers; B, if the ovule, e, have just appeared; C, section of ovule showing the sporogenous tissue and the epidermis. The pollen mother-cells usually separate before the first nuclear division occurs, and often have very thick cell-walls. The first nuclear divi-
+![]() A diagram illustrating the development of a flower in Naiais.
+Fig. 319.—A, Naiais striata. Section of young staminate flower, highly magnified; the axis is terminal and closely resembles the young ovule, both in position and in the position of the cells composing them. B-D, Liliae subitae. B, cross-section of young anther, showing the four lobes or pollen-sacs (× 300). C, part of an older pollen-sac, showing the large sporogenous cell (× 300). D, cell from the wall of a ripe anther, show-
+ing the "fibria" (× 600).
+
+
+ANGIOSPERM. # 858
+
+sion (Fig. 318) in the cell may be followed by a division-wall (many Monocotyledons), or more commonly the division-walls are not formed until after the second mitosis, and the resulting spores are of the tetrahedral type. In aquatic forms the spore-membrane may remain thin and uncuticularized; but usually there is an outer thickened peridium like that found in the spores of the Archeogoniates. The pollen-spore is enclosed in a thickened wall, which is called the mother-cell, the antheridal cell, is cut off (Fig. 318, E), and the nucleus of this subsequently divides into the two generative nuclei. In excep-
+tional cases —e.g. *Spargieum simplex* (Fig. 318, G) — a small sterile cell is cut off from the spore before the antheridal cell is formed.
+
+![]() A diagram showing the stages of nuclear division in a pollen mother-cell.
+A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
+
+**Fig. 318.** —A-C, *Allium Cuneatum*. First nuclear division of the pollen mother-
+cell (× 60). D-F, *Nasus densilis*. D, young pollen-sac (× 300). E, pollen-spore with cuticularized wall (× 600). F, pollen-sac with two generative nuclei and one sterile cell.
+G, *Spargieum simplex*, pollen-spore with sterile protoplasmic cell, pr (× 600).
+H, *Lathyrus odoratus*, germinating pollen; x, generative nucleus.
+
+The anther is usually composed of four pollen-sacs, and the walls of the nearly ripe sporangium consist of three layers of cells, of which the inner one at maturity becomes more or less completely disorganized. The outer layer consists of a few cells whose walls thicken to form bands ("filuris"), which are hygroscopic, and by their contraction effect the deliquescence of the pollen-sacs. They closely resemble the similar spiral thickenings found in the pollen-
+sacs of many other plants, such as *Equisetum*. Equally within the three layers of cells there lies a wall of the sporangium is a layer of tapetal cells, which is broken down before the division of the spores begins.
+
+B A
+
+354
+BOTANY
+
+The Ovule
+
+The macrosporangium, or ovule, in many of the lower Angiosperms (many Araceae, Peperomia), is formed directly from the apex of the floral axis, as it is in Taxus. Usually it is an outgrowth of the carpel. In either case the tissue from which it grows is called the Filamenta. The development of the ovule is very similar to that
+
+![]() A-D, Ficus ficifolia. Development of the ovule. A, section of very young ovule, formed from the axis of the shoot, showing the sub-epidermal archesporial cell (x 800); oar, the carpel; b, an older ovule, with the first integument, in', and the second integument, in", formed; c, a mature ovule, with two integuments; d, tapetal cell and spergous cell both divided, the latter into three. D, young ovule immediately after fertilization.
+
+of the Gymnosperms. Sometimes but a single integument is present, but more commonly there are two. When the growth of the ovule is alike on all sides, it is symmetrical, "sect," or "orthotropous"; where growth is stronger on one side it is bent over, "anatropous." More rarely it is "Campylopterus" or "Campylothorax."
+
+The archesporium can usually be traced back to a single hypoder-
+mal cell (Fig. 319). This may at once give rise to the embryo-sac.
+
+E
+![]() E, Ficus ficifolia. Section of mature ovule showing embryo-sac.
+![]() O, Ficus ficifolia. Section of young ovule showing embryo-sac.
+![]() D, Ficus ficifolia. Section of mature ovule showing embryo-sac.
+![]() C, Ficus ficifolia. Section of young ovule showing embryo-sac.
+![]() B, Ficus ficifolia. Section of young ovule showing embryo-sac.
+![]() A, Ficus ficifolia. Section of young ovule showing embryo-sac.
+![]() T, Ficus ficifolia. Section of young ovule showing embryo-sac.
+![]() in', Ficus ficifolia. Section of young ovule showing embryo-sac.
+![]() in", Ficus ficifolia. Section of young ovule showing embryo-sac.
+![]() ma, Ficus ficifolia. Section of young ovule showing embryo-sac.
+![]() ant, Ficus ficifolia. Section of young ovule showing embryo-sac.
+
+ANGIOSPERM.E 866
+
+(Tulip), but usually it divides by transverse walls into a row of 2-4 cells. Sometimes (Rosa liliacea, Arisaema triphyllum) there may be several of these aperogenous cells.
+
+The primary embryo-sac, generally has cut off from it an outer cell, the tapetum, which, by further division, gives rise to the tissue at the apex of the nucellus. The inner cell may at once form the embryo-sac, but more commonly divides into two or more cells, one of which later fuses with the others, and destroys them. It may ultimately destroy the whole of the nucellus except the apex, and forms the single large macroproc, or embryo-sac.
+
+The primary nucleus of the embryo-sac divides, and in the typical Angiosperms (Fig. 320) one nucleus moves to each end of the embryo-
+![]() A diagrammatic longitudinal section through a young angiospermous embryo-sac.
+320
+A. A. Narcissus tazetta, young embryo-sac with nuclei.
+B. Older embryo-sac with four nuclei.
+C. Diagram of typical angiospermous embryo-sac,
+at the apical end of the ovule.
+D. Diagram of typical angiospermous embryo-sac,
+and the egg-c., at the lower (dakhanal) end, the three antipodal cells, out; pn, the two polar nuclei; sy, the synergid; ant, the antipodal end;
+o, the egg-nucleus; o', the egg-cell; o", the egg-c., which contains sixteen free nuclei, and all shown in the sections (x 800).
+sac.
+The upper end is the micropylar end, the lower the chalazal, or antipodal end. Each nucleus then divides twice, and of the four nuclei at each end one moves toward the centre of the embryo-sac, where they fuse with each other to form a single nucleus.
+This fusion of the polar nuclei usually occurs before the fertilization of the egg-nucleus, but it may not occur until afterward. The three micropylar nuclei become invested with thin cytoplasmic membranes,
+and one of them is the egg-cell (o), the other two being known as Synergids. These are surrounded by three large green cells,
+the antipodal cells, which, unlike the cells of the egg-apparatus,
+very often develop a cellulose wall.
+
+Peperomia.--The genus Peperomia (Fig. 320 D) shows a marked de-
+parture from the other Angiosperms in the development of the gameto-
+
+356
+BOTANY
+
+phyte. The primary nucleus of the embryo-sac divides into sixteen,
+instead of eight, nuclei, and these nuclei are uniformly distributed
+through the peripheral cytoplasm, instead of forming a definite egg-
+apparatus and antipodal cells. In this respect the gametophyte of
+Perovskia is similar to that of the other members of the family Campanulaceae,
+and still more the condition found in the mature embryo-sac of Gnetum.
+As in Gnetum, apparently any nucleus may become differentiated to
+form that of the egg. In Perovskia no polar nuclei are developed,
+but after fertilization several (usually eight) of the nuclei fuse into
+one very large nucleus, which by division gives rise to the endosperm,
+or secondary proembial tissue.
+
+The Antipodal Cells
+
+The antipodal cells generally remain unchanged, and apparently
+take little part in the further development of the embryo-sac. There
+
+![]() A diagram showing the structure of an antipodal cell.
+
+Fig. 321. — A, Naius ferrula. Pollen-tube entering the embryo-sac (× 70); pt., pollen-
+tube; s., synergids; o., egg. B, Spermacium simplex, embryo; em., surrounded by
+the young endosperm-cells; en., free endosperm nuclei (× 300).
+
+are, however, many exceptions to this. Thus in most Grasses the number of antipodal cells is much increased, and they become large
+and conspicuous, and apparently play a part in some manner in the nutri-
+tion of the developing embryo-sac and embryo. A similar condition
+has been observed in many Compositae, and the very large antipodal
+cells of some Ranunculaceae show a division of the nucleus, although
+no cellular differentiation has taken place. This is also true of the case in
+that of Spermacium simplex (Fig. 322), where the three small antico-
+dal cells of the unfertilized embryo-sac subsequently give rise to a
+mass of one hundred and fifty or more active cells.
+
+Pollination
+
+The pollen-spores are sometimes so placed that they fall sponta-
+neously upon the stigma of the same flower. More commonly cross
+
+ANGIOSPERM. E
+
+pollination takes place, the pollen of one flower being carried to the stigma of another, either by the wind or by insects.
+
+The germination of the pollen-spore is stimulated by the secretion usually from the stigma. This process may be induced artificially by placing the pollen in a solution of sugar. The pollen-tube is sometimes emitted within a few minutes, and its growth is often extremely rapid. Either before or after germination has begun the generative nucleus divides into two, and each of these enters a developing tube, probably by the action of one of the cytoplasm, which are very active in the growing pollen-tube. The latter grows rapidly.
+
+![]()
+A: A section of distal end of embryo-sac, showing two of the antipodal cells and the endosperm cell.
+B: Longitudinal section of the developing endosperm (× 300).
+C: First cell-formation in the endosperm, surface view (× 300).
+D: Two sections of the antipodal cells after fertilization of the egg (× 400).
+
+
+Fig. 251. — Sporopollenanum. A, section of distal end of embryo-sac, showing two of the antipodal cells and the endosperm cell. B, longitudinal section of the developing endosperm (× 300). C, first cell-formation in the endosperm, surface view (× 300). D, two sections of the antipodal cells after fertilization of the egg (× 400).
+
+through the style, where it is developed a special "conducting tissue," whose cells contribute the material necessary from the growth of the pollen-tube, which grows precisely like the hyphae of a Fungus through the tissues of its host. The conducting tissue is continued into the pollen-tube itself, and this is thus able to grow along this the pollen-tube advances until it reaches the micropyle of the ovule, into which it penetrates, and pushes through the tissue at the apex of the enucleus and enters the embryo-sac. In most instances it grows through one of the synergid, which is destroyed, and discharges one of the generative nuclei into the egg, where it fuses
+
+857
+
+358
+BOTANY
+
+with the egg nucleus. The second generative nucleus is discharged into the cavity of the embryo-sac, and sometimes, at least, fuses with the endosperm-nucleus, formed by the union of the polar nuclei.
+
+**Homologies of the Embryo-sac**
+
+The embryo-sac represents the macrospore of the heterosporous Pteridophytes, and the structures developed within it, the gametophyte. From a comparison of the condition found in Peperomia with that of the Pteridophytes and Gymnosperms, it is probable that the egg-cell is homologous to that of the Pteridophytes. In the typical Angiosperms the two synergids may probably be considered as also, potentially, one-celled archegonia. All of the other nuclei, endosperm-nuclei, etc., are homologous with those of the gametophyte. The fusion of the nuclei preliminary to the formation of the endosperm is probably a stimulus to further active division, but can hardly be considered a true fertilization, as is sometimes done. This is also true of the fusion of the second generative nucleus with the egg-nucleus. The following facts are interesting experiments have been made in hybridizing Indian-orn, which show that the endosperm of the grains resulting from cross-pollination combines the characters of the parent plants, indicating that in all probability the endosperm-mutum had united with one of the pollen-nuclei.
+
+**The Embryo**
+
+The embryo of the Angiosperm shows a good deal of variation. It may remain undifferentiated until after germination, or it may become so large as to completely fill the cavity of the ripe seed. Usually, but not always, a suspensor is developed, as in the Gymno-
+sperms.
+
+**Polyembryony** — Polyembryony, or the development of several embryos from a single ovule, which is the rule in many Conifers, is unusual in Angiosperms, but there are numerous exceptions. Thus in Citrus (Orange and Lemon) several embryos are not infrequently found in one ovule. In some species of Iris these embryos arise apogonously, by a budding of the tissue surrounding the embryo-
+sac, and the same is true in Funkia. Jeffrey (15) has described in *Erythronium Americanum* the development of several embryos from a single ovule. In *Corydalis*, *Aquilegia*, and *Ranunculus* mono-
+sperma.
+In *Iris Sibirica*, and some Leguminosa, polyembryony has been referred to as a fertilization of the synergids, and in *Allium odorum* embryos may be developed apogonously from the antipodal cells.
+
+ANGIOSPERM.E 330
+
+The Endosperm
+
+After fertilization has been completed, the endosperm-nucleus divides. This is sometimes followed immediately by the formation of a division wall (Monotrope, some Araceae), and the embryo-sac is at once filled with a continuous mass of tissue. Much more commonly (Fig. 15) the endosperm is composed of repeated nuclear division resulting in many free nuclei lying in the cytoplasm, while the centre of the embryo-sac is occupied by a large sap-cavity. Sooner or later, walls are formed between the nuclei, precisely as in the formation of the protallial tissue in the Gymno-
+sperms. The endosperm thus becomes thick, and finally com-
+pletely fills the embryo-sac, and the small embryo is imbedded in a mass of cells, filled with starch or other nutrient matter. If the embryo is large, it often fills the cavity of the endosperm; in an early period, however, the embryo is very small and immature. In such cases, there is a large suspensor developed, and the embryo receives nourishment directly from the outer tissues of the nucellus. Very rarely, as in the Coconut, the sap-cavity of the large embryo-sac remains empty.
+
+Sometimes the embryo-sac remains small, and the development of the endosperm is slight. In such cases (Peperonia, Nymphaea), the cells of the nucellus become filled with food materials, and take the place of the endosperm. This tissue is the "Periperm."
+
+The Seed
+
+The integument (testa) of the seed may remain thin, as in
+the kernel of various stone fruits (Cherry, Peach, etc.), but usually it is hard and the ripe seeds have no further protection. Sometimes there are outgrowths of the integument forming hairs, or wings, as in the apple and pear. These are useful to man, and these assist in
+the distribution of the seeds by the wind. More rarely, as in some
+Araceae, the outer part of the integument is pulpy.
+
+The Fruit
+
+In the Angiosperms the stimulus exerted by pollination extends beyond the transformation of the ovule into a seed. Sometimes, at
+the time of pollination, there is rudimentary (Oak, Orchid-
+aceae), and it develops during the slow growth of the pollen-tube through the tissues of the pistil. In all cases the carpels are stimu-
+lated into growth, and keep pace with the development of the endocarp.
+Seed about which they form a protective envelope. This structure
+thus formed is the Fruit, using the term in its strict sense. The
+
+300
+BOTANY
+
+fruit of the Angiosperma (Figs. 332-337) is extremely varied, and may be either a dry fruit, like a grain of Wheat or the pod of a Lily, or it may be a fleshy fruit, like the berry of a Currant, or the stone fruit (Drupe) of a Cherry or Plum. Besides these true fruits, there are various other kinds of fruits which are not true fruits, but which is not the product of the carpels. Such are the Fig, where the edible portion is the enlarged hollow stem, within whose cavity are born numerous small flowers, producing one-seeded fruits. Similarly the *acacia* is a fruit produced by a flower which has been enclosed in the fleshy receptacle or enlarged apex of the floral axis. The development of edible fruits in the Angiosperms is connected with their distribution by animals.
+
+**Germination**
+
+The germination of the seed is like that in the Gymnosperms. In Angiosperma also, chlorophyll may be developed in the cotyledons before they are withdrawn from the seed. Where the embryo fills the seed, the first leaves appear through the micropyle, and then grow out through the micropyle, and the second leaves, which are already indicated in the embryo, soon unfold. The cotyledons may remain permanently within the seed, or they may be used as food assimilating organs. When the embryo in the ripe seed is small, it grows for some time at the expense of its own food reserves until it pushes out of the seed. The cotylle-dons are usually decidedly simpler in structure than the leaves formed later.
+
+**The Stem**
+
+The stem-apex in the Angio-sperma never shows a single apical cell, but the primary tissues are all separated by cells (Fig. 332). The epidermis is continuous, and below this is the primary cortical tissue, the periblem, while the central part forms the plerome-cylinder. It is not always possible to separate the two latter at the apex, but the dermatogen is always clearly defined.
+
+![]() A diagram showing a longitudinal section through the stem-apex of a young plant.
+Fig. 332 - *Neina ferrula*, longitudinal section through the stem-apex of the young plant (300).
+
+301
+
+ANGIOSPERM. E
+
+301
+
+In a very small number of Angiosperms, probably all reduced types, there is no properly developed stem, the sporophyte approaching the condition of a thallus. Such are the minute aquatic Lemnaceae, the Ranunculaceae and Ranunculaceae, which are endophytic.
+
+![]() Fig. 304. — Runners of Strawberry. (After BAILEY.)
+parasites, resembling Fungi in their habits, and the Podostemonaceae, aquatic Diocotyledons, some of which might be mistaken for Alga.
+
+Branching. — Usually the stem is well developed and shows great variety. The shoot may be unbranched (Corydorea, American Trillium), or it may commonly branch freely, either to form
+
+![]() Fig. 305. — Tubers of Potato. (After BAILEY.)
+flowers or for secondary vegetative shoots. True dichotomous branching is rare (Zamiocelilia), and, with few exceptions, lateral members arise in the axils of leaves. If the stem develops little wooly tissue, it is said to be herbaceous; if wood is well developed, it is "woody" or "ligneous."
+
+-
+
+362
+BOTANY
+
+**Modifications of Stem.** — Some of the more striking modifications of the stem in Angiosperms (Figs. 324-328) have been described in a former chapter. These include the *various* subterranean forms (bulb, Corm, Tuber, Rhizome), which are reservoirs or re-servoirs; *root* Stolons, and similar prostrate stems, are im-portant modes of propagation; while twining stems and the *stem-bendrils* are additional factors for assisting plants to reach the light. The strong thorns of such trees as the Honey-locust (Gleditschia) and the Hawthorn are stem-structures which are presumably protective.
+
+The development of aerial stems where the water supply is deficient, is connected with a reduction or complete suppression of leaves, and is obviously to reduce the surface exposed to evaporation.
+
+![]() Fig. 326.—Stem-bendrils of Cucumber. (After BAILEY.)
+
+**The Leaf**
+
+The various forms of foliage-leaves, already described in Chapter II., are found among the Angiosperms. The Dicotyledons offer much greater variety in this, as they do in other respects, than do the Monocotyledons.
+
+**Modified Leaves.** — The leaf, like the stem, may be greatly modified for special functions. Scale-leaves, such as those in sealy bulbs, or inter-bud scales on the buds only, as may be readily seen in some instances where there are transitions between them and the typical foliage-leaves.
+
+In submerged aquatics, like Naiads or Myriophyllum, the leaves either are reduced to scale-like structures, or else the epidermal cells are not cuticularized, nor are stomata developed. In xero-phyles, i.e. plants of arid regions, the leaf surface is reduced, and sometimes the leaves are very thick and fleshy, as in species of Agave and Yucca. In these plants, not needing organs for photo-synthesis, have the leaves rudimentary.
+
+Spines, tendrils, and the traps like those in the Pitcher-plants and Bladder-weed, are also foliar structures.
+
+ANGIOSPERM.A
+
+368
+
+The Floral Leaves
+
+The peculiar leaves making up the floral structures are, next to the seeds, the most characteristic structures of the Angiosperms. Besides the sporophylls and perianth-leaves, we may include under this head of floral leaves the showy bracts which occur in many plants, surrounding the inflorescence and often performing the functions of the petals. Such are the bracts of the Arrow (Genus Araceae), the bracts of the showy Dogwood (Genus Florida), of many species of Euphorbia, etc.
+
+The Root
+
+The root in the Angiosperms, like the stem, never shows a single apical cell, but the tissues of the apex consist of two or more layers of primary meristem, showing some variation in different cases. The branching of the roots is always monopodial, and the secondary branches arise from the pericycle, as they do in the Gymnosperms.
+
+The primary root of the embryo may persist as a tap-root (Radish, Dandelion, etc.), or it may develop lateral roots, a condition always found in the Monocotyledons, and common in many Decotyledons.
+
+The modifications of roots are similar to those of the stem. Roots may be enlarged for purposes of storage, a condition found in many plants useful to man (vegetables (Beet, Turnip), etc.). Aerial roots are developed, which serve for support, -- e.g. those developed near the base of the stem in Indian-corn, and to very much larger ones of many tropical trees (Banyan, Mangrove, etc). Aerial roots also serve for tendrils, -- e.g. Ivy, Poison-ivy (Rhus toxicodendron), etc., -- and in some epiphytic Orchids and Araceae they absorb moisture from the air.
+
+Structure of the Flower
+
+The more primitive types of flowers have all the parts separate, and may be reduced to little more than a single carpel or stamen. The floral envelopes may be entirely absent (Perepomia, Saururus), but there are usually rudiments, at least, of a perianth.
+
+![]() Fig. 327. - Raceme of Lily-of-the-valley. (After Huxley.)
+
+364
+BOTANY
+
+Somewhat more specialised flowers are the "Apocarpous" flowers with well-developed perianth, such as Asimina (Fig. 313), but all of the floral leaves quite separate. These simple flowers, too, may have the number of parts indefinite, and are often radially symmetrical, or actinomorphic.
+
+In these flowers, because of specialisation, the parts become definitely fewer, and there is tendency to reduction in the number of parts, and to cohesion of the floral leaves. Thus in the members of the Lily family the flowers are of several types, in which the three carpels are united into a compound pistil. In most Diotyledons there is also a difference in the character of the sepals and petals and the former are united together into a cup-shaped or tubular calyx, as in Dioscorea.
+
+![]() A and B - Diagrams showing different types of flower structures.
+
+Fig. 320. A, umbel of Aralia racemosa. B, head of Antho-
+mis cucullata; r., ray-flower.
+
+In such highly specialised flowers as the Orchids (Fig. 338, C), the reduction and cohesion of the parts is carried to the extreme. Of the six stamens only two remain free, while the other four are left, and the base of the perianth-tube is coherent with the base of the carpels. Moreover, the single stamen is united with the upper part of the pistil so that this is known as "Gynostemium," or "Gynostemium." Where all of the parts are free from the ovary the flower is "Hypogynous"; where the ovary is more or less completely adherent to the receptacle it is "Epigynous."
+
+Fig. 321. - Spike-like flower of Piastrina.
+
+In the reduction of parts in the diotyledonous flower the carpels are the first to diminish, the num-
+ber of carps being less, as a rule, than that of the other floral leaves. Where there is a complete reduction to symmetry, like the lipped flowers of the Foxglove or Sage, in The less
+
+![]() Illustration showing a flower with reduced stamens and carpels.
+
+ANGIOSPERM.Æ 365
+
+specialized forms related to these, like the Morning-glory or Nemo-
+phila, the flowers are actino-
+meral, and the number of
+stamens is the same as the
+corolla lobes.
+
+In the Compositae (Daisy,
+Sunflowers), which are
+usually considered to be the
+most specialized of the Di-
+cyledonae, there is often a
+division between the
+flowers. In a large number
+of them there are developed
+the so-called "Ray-floræ" (Fig. 328)
+quite sterile, and serve merely
+to make the inflorescence
+conspicuous.
+
+All of these modifications
+of form are associated with
+adaptations to cross-pollina-
+tion, and with them are to
+be classed the extraordinary
+development of color and
+scent in flowers.
+
+The Inflorescence
+
+(Figs. 327-331.) - A flower may be formed singly at the end of
+the shoot, as in most species of Narcissus, Trillium, Sanguinaria,
+etc. Such a floral axis is called a Scopa. Much more commonly,
+
+![]() Fig. 320.—Cyme of Tulip Americana.
+(After BAKER.)
+
+![]() Fig. 321.—Compound cyme of Hydrangea arborescens.
+
+366
+BOTANY
+
+![]() A plant with a long, slender stem and a large, flat, green leaf at the top.
+A
+
+![]() A plant with a long, slender stem and a small, pointed leaf at the top.
+C
+
+![]() A plant with a long, slender stem and a small, pointed leaf at the top.
+D
+
+![]() A plant with a long, slender stem and a small, pointed leaf at the top.
+F
+
+![]() A plant with a long, slender stem and a small, pointed leaf at the top.
+E
+
+![]() A plant with a long, slender stem and a small, pointed leaf at the top.
+B
+
+**Fig. 328. — Dehiscent dry fruits.**
+A. Pae (capsule).
+B. Aquilegia Canadensis (bilobe).
+C. Capsula burra-pastoris (elliptic).
+D. Fimia muculata (capsule,
+opening by three valves).
+E. Stylophorum diphyllum (capsule).
+F. Agrimonia eupatoria (capsule opening by two valves).
+
+Rowsers are arranged in an "Inflorescence." There are two principal types of inflorescence, the "Race-mose" and the "Cymose," which, in turn, have various subdivisions.
+
+In the "Race-mose," the axis of the floral shoot continues to grow indefinitely, giving rise to a varying number of lateral shoots, developing in opposite succes-
+sion, the youngest being nearest the apex. Its simplest form is the Ba-
+ceme (Fig. 327), where single stalked flowers are strung along the central axis like old-fashioned lanterns.
+If the flowers are sessile, as in the Plantain (Fig. 328) or Pepper family, we have a "Spike"; if they are very numerous and crowded together, "Umbel" (Fig. 329, A) or a "Head," as the flowers are respectively stalked or sessile.
+
+In the cyme, or symmetrical inflo-
+rescence, each flower is terminal on its axis, and the lateral axes grow more
+
+![]() A plant with a long, slender stem and a small, pointed leaf at the top.
+em
+
+**Fig. 329. — Indehiscent dry fruits.**
+A. Taraxacum officinale, schene.
+B. Euphorbia peperomia.
+C. Zea Mays, corn.
+D. Fraxinus americana,
+"key."
+E. Molus rotundifolia, schimoser.
+
+![]() A plant with a long, slender stem and a small, pointed leaf at the top.
+A
+
+![]() A plant with a long, slender stem and a small, pointed leaf at the top.
+B
+
+![]() A plant with a long, slender stem and a small, pointed leaf at the top.
+C
+
+![]() A plant with a long, slender stem and a small, pointed leaf at the top.
+D
+
+![]() A plant with a long, slender stem and a small, pointed leaf at the top.
+E
+
+ANGIOSPERM. 367
+
+vigorously than the main axis. Thus the older flowers are uppermost or central. There are three types of cymose inflorescences:
+(1) The Monoecium; there each partial axis produces a single branch. Where these all arise on one side, the heli-
+cold cyme, such as occurs in Heliotropium, Mentha, etc., is produced.
+(2) The Dichasium; two branches are produced from each
+axis. (3) The Polycasium; each axis produces more
+than two branches.
+
+The Fruit
+
+The fruits of Angio-
+ sperma may be first
+ visited into syncarpous
+ and syncarpous fruits.
+ The first are those derived
+ from a single carpel (e.g.
+ Bocconia), the second from two or more united carpels,
+ parts, the seed and the Pericarp, or wall.
+ The principal types of fruits are the following
+ (Figs. 332-337):
+ I. A dry fruit with a dry pericarp opening in regularly
+ manner. The capsule opens most frequently by longitudinal fissures which follow either the line of separa-
+ tion of the carpels (septal or loculical), or each carpel is split longitudinally (loculical). More rarely the capsule opens by pores (Papaver) or by a lid (Jeffersonia). The "Follicle" (Aqu-
+
+![]() A diagram showing a fruit with a single carpel.
+A
+
+![]() A diagram showing a fruit with two carpels.
+B
+
+![]() A diagram showing a fruit with three carpels.
+C
+
+![]() A diagram showing a fruit with four carpels.
+D
+
+Fig. 334. - Indebent succulent fruits. A, sec-
+tion of young cherry (drupe). B, Persimmon,
+showing the two carpels of the drupe to be compound. C, Solanum dulcamara (berry).
+D, section of young apple (pome).
+
+Fig. 335. - Acer of Quercus
+manouropus. (After
+Bailey.)
+
+Fig. 336. - Section of an Apple (pome). (After
+Bailey.)
+
+by longitudinal fissures which follow either the line of separation of the carpels (septal or loculical), or each carpel is split longitudinally (loculical). More rarely the capsule opens by pores (Papaver) or by a lid (Jeffersonia). The "Follicle" (Aqu-
+
+368
+BOTANY
+
+Legia) and "Legume" (Bean, Pea, etc.) are examples of apocarpous capsules.
+
+II. Dry, indehiscent fruit. These are fruits with hard, dry pericarp, which does not sep-
+arate from the seed (e.g., Acacia, Eucalyptus), Acorna, the "Caryopsis" (grain) of Grasses, the seedlike fruits (Achenes) of the Com-
+posite, are examples of these. Differing from these is the "Utricle" - e.g. species of Caper.
+III. Schizocarp. A dry fruit composed of several indehiscent carpels which separate from each other - e.g. Hollyhock, Umbelliferae.
+IV. The Stone-fruit or Drupe. The Pome,
+Gooseberry is an example, and Melons and
+Pumpkins show much the same structure on
+Fig. 357. Section of a
+Fig. 357. Section of a
+bellow receptacle con-
+taining many flowers,
+each of which produces
+does a single com-
+plete fruit (stone).
+(After RANLY.)
+
+The Stone-fruit or Drupe. The Cherry,
+Plum, Peach, etc., are familiar examples of
+stone-fruits. In the inner part of the endocarp
+forms the "stone," which is enclosed within the stone. Among the Monocotyledons, the Date and Coconut offer examples of stone-fruits.
+
+![]()
+A: A syngamous flower with symmetrical sessile ovule (Syngamia). B: Syngamous flower of Liriope subspicata. C: Syngamous syngamous flower of an Orchid (Orchis mascula). D: Syngamous flower of a grass (Poaceae). E: Syngamous flower of a legume (Lathyrus odoratus). F: Syngamous flower of a legume (Lathyrus odoratus).
+
+
+Fig. 358. - Specialization of the flower. A, Syngamous flower with symmetrical sessile ovule (Syngamia). B, Syngamous flower of Liriope subspicata. C, Syngamous syngamous flower of an Orchid (Orchis mascula). D, Syngamous flower of a grass (Poaceae). E, Syngamous flower of a legume (Lathyrus odoratus). F, Syngamous flower of a legume (Lathyrus odoratus).
+
+368
+
+ANGIOSPERM.* 309
+
+**Classification of Angiosperms**
+
+The Angiosperms agree so closely in their fundamental structure as to leave little question that they form an entirely natural class.
+With very few exceptions they really fall into two series, Monocotyledons and Dicotyledons. In the former, the embryo has the first leaf alternate; i.e. a single cotyledon is developed. In the Dicotyledons, the cotyledons are opposite.
+
+SUBCLASS I. MONOCOTYLEDONES
+
+The Monocotyledons are much less numerous, and, on the whole, less specialized, than the Dicotyledons. There is greater uniformity in the leaves, and the structure of the flowers also shows less variation.
+
+The simplest sporophyte is found in the Lemnaceae, minute, floating aquatics in which the sporophyte is, in Wolfia, a globular or oval mass of cells, with a single root-like projection, or stolon, and producing roots in Lemma. It is not entirely clear whether the plant body in the Lemnaceae is mainly a leaflike stem, or a foliar structure. The largest Monocotyledons are the Palms, some of which grow as tall as 100 feet. They are high with the largest leaves found in any plants. The Rattan Palm (Calamus) have slender, climbing stems of even greater length.
+
+The Monocotyledons are universally distributed; some forms, like the Green Algae and certain aquatic Spermatophytes are Monocotyledons, which play an important rôle in the vegetation of marshes. The Reed, Sedges, Bulrushes, etc., are all Monocotyledons, and the same is true of the Pondweeds and most other types of aquatic plants. The Monocotyledons include a number of characteristic types, especially in the Tropics. Of these marine forms, Zostera and Phyllospadix may be mentioned as American genera. Some of the fresh-water aquatic species occur in great abundance in our streams and ponds. The Water-lily ("Water-hyacinth") is one of them. The latter, a floating plant, has become very troublesome in some of our southern streams, where it was introduced from the Tropics because of the beauty of its flowers. Of the terrestrial Monocotyledons there are many species widely distributed. These are almost the only terrestrial monocotyledonous plants which are sufficiently abundant, at least in temperate climates, to give a decided character to the vegetation of any region. In the swamps and marshes of Florida and Georgia there are many Yucca, and related forms are abundant enough to be very conspicuous. This is especially true of the latter in dry regions like the deserts of Arizona and Southern California, where the Yucca and
+
+![]() A page from a book about angiosperms.
+
+370
+BOTANY
+
+Agaves, next to the Cacti, are the most conspicuous plants. Para-
+sites and saprophytes are of rare occurrence among the Mono-
+cotyledons, and are confined to the Orchidaceae and the related
+Burmanniaceae.
+
+The Gametophyte
+
+With few exceptions, the gametophyte conforms to the ordinary angiospermous type. The ripe pollen-spore contains either one or two generative nuclei, besides the single polar nucleus. In some cases (e.g., in the Liliaceae) two have been
+observed, in Saxifragaceae simplex, and exceptionally in Lilium trionum, a small
+sterile cell, which possibly represents a protodermal cell like that in the micro-
+spores of the ferns. The formation of the pollen-nucleus has not been re-
+corded for Lilium auratum.
+
+The embryo-sac may arise directly from the primary hypotrophous cell. This is the case with the Liliaceae, but in many other families the cell divides, by a transverse wall, into an outer tapetal cell (Fig. 319) and an inner one, which may de-
+velop at first as a series of cells, one of
+which destroys the others, and becomes the embryo-sac.
+
+In Arisaea triphylla, and this not probably may be found in some other
+Araceae, the embryo-sac is formed by a transverse wall dividing the original
+nucleus into four cells, one of which grows faster than the others. This cell divides
+once more by a transverse wall, and the lower cell is the embryo-sac.
+
+The ovule is generally composed of three layers. These are found in
+Angiosperms; but in many Grasses the three original antipodal cells generally increase to six or eight. In some species of Iris and Zantedeschia they are six at
+the time it is fertilized. In abnormal cases in Naias and Zannichellia and in
+some Araceae indications of an increased number of nuclei in the unfertilised embryo-sac have been observed. Further research in the lower Monocotyledons will probably bring to light other departures from the typical structure.
+
+Pollination
+
+Pollination may be effected by the wind (Palma, Grusses, etc.), by
+water, or by insects. The adaptations for water pollination are of two kinds.
+In forms with submerged flowers (Zostera, Naias), the pollen
+is thin-walled, so that the former external segment, so that the
+pollen-grain is readily attracted to it when it comes in contact with it. In Vallinaria (Fig. 361) the pistillate flower opens above the surface of the water; and the minute male flowers open below it. The pollen-grains adhere to the surface, where they expand and float about until the open anthers come in contact with the stigmas of the female flower, upon which
+the pollen is deposited.
+
+Monocotyledons have showy flowers, like the Lilium, Iris, Orchidæ,
+etc., are often pollinated (insect-pollinated); and some, like species of
+Iris, and many Orchids, are quite dependent upon insects to insure
+pollination.
+
+Sometimes a long interval elapses between pollination and fertili-
+
+ANGIOSPERM. # 371
+
+zation, as is the case in many Gymnosperms. This is especially true of many Orchids, where the whole development of the ovaules may take place subsequent to pollination.
+
+![]() A, B, C, D, E, F
+Fig. 300. -- *Nolias flexuosa*. Development of embryo. A-E, longitudinal sections (*x 300). F, transverse section of older embryo (*x 300); *su*, suspensor-cell;
+*ks*, lateral suspensor-cells.
+
+The Embryo
+
+The Embryo (Figs. 330-341) may remain very rudimentary, as in the Orchids, where it is a nearly globular mass of perfectly undifferentiated tissue. On the other hand, the embryo may be large, and completely fill the embryosarcum, and be surrounded by a suspensor, and the organs of the young sporophyte are well developed.
+
+The fertilized egg usually divides by a transverse wall into two cells, of which the basal one, which is in contact with the upper cell, remains stationary and divides further, but may become much enlarged, and serves as an organ of absorption. The other cell divides again into two cells, one of which enters into the young embryo, or it may undergo several transverse divisions before it leaves the suspensor with the embryo at the apex (Fig. 300). The latter, in typical cases, develops the root first; while in others the apical portion, while the root arises from the region which is in contact with the suspensor, grows out from its base of origin, and is first recognizable at a late stage in the development of the embryo. In this respect the Monocotyledons resemble Lecoces.
+
+![]() A, B, C, D
+Fig. 300. -- *Euterpe flexuosa*. Older em-
+bryon. (*A*, *x 300); (*B*, *x 700*); *cot*,
+coelocystid; *sr*, stomatoid; *r*, root;
+*su*, suspensor.
+
+In this respect the Monocotyledons resemble Lecoces.
+
+372
+BOTANY
+
+Less frequently the stem-apex arises from the terminal segment of the young embryo, and the single cotyledon is borne at its side. This occurs in the Alliums and Zamiocelis (Fig. 341), and has also been described for the Dioscoreaceae and some other Monocotyledons. In the embryo in these forms is intermediate in character between the typical Monocotyledons and the Dicotyledons.
+
+Sometimes a suspen-
+sor is present, consist-
+ing (some Araceae and
+Gramineae), and
+sometimes lacking.
+In the section of the regular quadra-
+tary cells, found in
+the Pteridophyta,
+The absence of a suspen-
+sor is associated with the early investment of the embryo by the endosperm-cells.
+
+**The Endosperm**
+
+The primary endosperm-nucleus always divides, and usually gives rise to many secondary nuclei before any cell-walls appear. Where the embryo develops early, as in Naias (Fig. 342), the endosperm-nucleus is large, but where it is largely developed, as in Naias *falcata* the endosperm is formed from the upper one only of two primary nuclei, which remain as a large endosperm-
+nucleus. The lower one remains undivided, but increases very much in size. The endosperm is usually formed by free-cell formation, — that is, by simultane-
+ous formation of new cells from existing ones. The cells are derived from cellular tissue proceeding from the periphery towards the centre of the sac (Fig. 322, B). In some Araceae, cell-walls extending across the cavity of the embryo-
+are formed from the endosperm, and the embryonic-is from the first completely filled with the prothallial tissue.
+
+Where the endosperm is present in the ripe seed, its cells are filled with starch, oil, or other nutritive substances. In other cases — e.g.
+many Palma (Date, Phytoliphasa) — the reserve food is in the form of cellulose, developed in the greatly thickened walls of the en-
+dosperm-cells.
+
+**Germination**
+
+The cotyledon may become a foliage-leaf (Onion) (Figs. 342-344); but more commonly, as in the Grasses and Palma, the cotyledon re-
+mains permanently within the seed, acting as an organ for the ab-
+sorption of the food-materials in the endosperm. By the downward
+
+![]() A diagram showing a cross-section of an embryo.
+372
+
+**Fig. 341.—A., Zamiocelis palustris, section of embryo (x 300). B., Zamiocelis palustris, section of embryo (x 300). In A., a suspensor is present; in B., it is absent. In both sections, a large endosperm-nucleus is present. In A., two smaller nuclei are present; in B., they are absent. In A., a large vacuole occupies most of the space occupied by the endosperm-nucleus; in B., it is reduced to a small vacuole. The lower nucleus remains undivided; in A., it becomes very large; in B., it remains small. The upper nucleus divides into two cells; in A., one cell remains undivided; in B., it becomes very large. The lower nucleus remains undivided; in A., it becomes very large; in B., it remains small. The upper nucleus divides into two cells; in A., one cell remains undivided; in B., it becomes very large. The lower nucleus remains undivided; in A., it becomes very large; in B., it remains small. The upper nucleus divides into two cells; in A., one cell remains undivided; in B., it becomes very large. The lower nucleus remains undivided; in A., it becomes very large; in B., it remains small. The upper nucleus divides into two cells; in A., one cell remains undivided; in B., it becomes very large. The lower nucleus remains undivided; in A., it becomes very large; in B., it remains small. The upper nucleus divides into two cells; in A., one cell remains undivided; in B., it becomes very large. The lower nucleus remains undivided; in A., it becomes very large; in B., it remains small. The upper nucleus divides into two cells; in A., one cell remains undivided; in B., it becomes very large. The lower nucleus remains undivided; in A., it becomes very large; in B., it remains small. The upper nucleus divides into two cells; in A., one cell remains undivided; in B., it becomes very large. The lower nucleus remains undivided; in A., it becomes very large; in B., it remains small. The upper nucleus divides into two cells; in A., one cell remains undivided; in B., it becomes very large. The lower nucleus remains undivided; in A., it becomes very large; in B., it remains small. The upper nucleus divides into two cells; in A., one cell remains undivided; in B., it becomes very large. The lower nucleus remains undivided; in A., it becomes very large; in B., it remains small. The upper nucleus divides into two cells; in A., one cell remains undivided; in B., it becomes very large. The lower nucleus remains undivided; in A., it becomes very large; in B., it remains small. The upper nucleus divides into two cells; in A., one cell remains undivided; in B., it becomes very large. The lower nucleus remains undivided; in A., it becomes very large; in B., it remains small. The upper nucleus divides into two cells; in A., one cell remains undivided; in B., it becomes very large. The lower nucleus remains undivided; in A., it becomes very large; in B., it remains small. The upper nucleus divides into two cells; in A., one cell remains undivided; in B., it becomes very large. The lower nucleus remains undivided; in A., it becomes very large; in B., it remains small. The upper nucleus divides into two cells; in A., one cell remains undivided; in B., it becomes very large. The lower nucleus remains undivided; in A., it becomes very large; in B., it remains small. The upper nucleus divides into two cells; in A., one cell remains undivided; in B., it becomes very large. The lower nucleus remains undivided; in A., it becomes very large; in B., it remains small. The upper nucleus divides into two cells; in A., one cell remains undivided; in B., it becomes very large. The lower nucleus remains undivided; in A., it becomes very large; in B., it remains small. The upper nucleus divides into two cells; in A., one cell remains undivided; in B., it becomes very large. The lower nucleus remains undivided; in A., it becomes very large; in B., it remains small. The upper nucleus divides into two cells; in A., one cell remains undivided; in B., it becomes very large. The lower nucleus remains undivided; in A., it becomes very large; in B., it remains small. The upper nucleus divides into two cells; in A., one cell remains undivided; in B., it becomes very large. The lower nucleus remains undivided; in A., it becomes very large; in B., it remains small. The upper nucleus divides into two cells; in A,,
+
+ANGIOPERMAE
+
+373
+
+growth of its base, the young plant may be forced deep down into the earth; and the first leaf to appear above the surface is the first
+
+![]() A diagram showing the stages of germination of Allium cepa.
+**Fig. 362.** — Allium cepa, stage of germination (After BAILEY).
+
+**Fig. 363.** — Allium cepa, early stage of germination (After BAILEY).
+
+**Fig. 364.** — Allium cepa, later stage of germination; the cotyledon is held in the ground; e, the second leaf (After BAILEY).
+
+foliage-leaf, and not the cotyledon. Where no endosperm is present, the food substances are stored in the cells of the embryo.
+
+The primary root, although often well developed, is of limited growth; and soon others arise, so that a cluster of roots is developed instead of the single tap-root met with in the Gymnosperms.
+
+Where the embryo is well developed, as it is in Naias or the Grasses, the young secondary roots are sometimes the early secondary roots, are present in the ungerminated embryo.
+
+The axis of the sporophyte may remain short, as in many bulbous plants, and in such cases the leaves when numerous are closely set about the thickened axis. In the Palms and some
+
+**Fig. 365.** — Fucus alboflos. A, Cross-section of outer layer of epidermis; B, cross-section of cortex with young vascular bundles; C, a single young vascular bundle (320).
+
+373
+
+374
+BOTANY
+
+treelike Liliaceae, — e.g. Yucca — the stem ultimately forms a trunk, which may in the latter increase in diameter as the plant grows older, but in the Palms rarely shows any thickening after the crown of leaves has been formed. In the former case the thickening of the stem does not begin until the crown of leaves is full grown, and then the elongating trunk remains of nearly uniform diameter throughout. Sometimes the stem is slender and freely branched — e.g. Zamiocelis, Potamogeton, Asparagus.
+
+![]()
+A B
+ph ph
+t t
+
+
+Fig. 368. — Iris Florencia. Vascular bundle from the scape (× 200). A, cross-section; B, longitudinal section; ph, phloem; t, tracheids; s, sieve-tube.
+THE MATURE SPOROPHYTE
+
+The Stem
+
+The internal structure of the stem is much the same in all Mono-
+cotyledons (Figs. 347, 348). Differing only in the presence of parenchyma, through which are scattered the numerous collateral vascular bundles, which never show the secondary thickening found in the stem-bundles of the Gymnosperms and Dicotyledons. These bundles are leaf-furrowed and in the stems like those of the Palms, and in such bundles surrounded by a sheath of cells, which act as mechanical or supporting elements, as the xylem of the bundles is always slightly developed and serves only for conduction. The other mechanical elements consist of hypodermal tissue, which may be collenchyma or fibrous tissue.
+
+375
+
+ANGIOSPERM. 375
+
+The vascular bundles (Fig. 346) have upon the inner side a group of trachyarch
+tissue, composed mainly of spiral or reticulately marked vessels, which are often
+of large size. Within this tissue is a layer of parenchyma, the phloem (phloëum), which
+is made up of similar elongated parenchyma, mingled with sieve-
+tubes.
+
+Monocotyledons are usually perennial plants, but in cooler regions
+the aerial shoots are sent up each year from the underground stem,
+which may be a rhizome (e.g. many Grasses, Iris Germanica, Iris
+Cinca, etc.), a scaly bulb (Lilium, Erythronium, etc.), or a corm
+(Gladiolus, Brodiaea). The aerial shoots are often of very brief
+duration, as in the Scilla, Tulip, etc., but the green shoots live
+only long enough to ripen the seeds and to produce the other
+substances which are stored up in the underground stem for
+next season's growth. When the growth of the aerial shoots is
+interrupted by prolonged cold, as in the Caper (Capitula),
+plants, the bulbs are small, and the growth of the new shoots
+is only in a small measure dependent upon the reserve-food stored up in the bulb.
+
+Sometimes the growth of the aerial shoots is extraordinarily rapid.
+Thus in some of the large species of Bamboo, the shoots attain a
+height of thirty to forty metres, this whole growth being completed
+within a few weeks' time, and a growth of nearly a metre has been
+recorded in less than four hours.
+
+Secondary Thickening. Where the stems are perennial, as in
+Yucca, Dracaena, and Pandanus, there may be an increase in diamete-
+r, such as occurs in Gymnosperms, but it is caused in a different
+way. There is an increase in thickness with age along one out
+section of the stem (Fig. 340) shows this typical monocotyledonous
+structure, with numerous scattered bundles. In the outer cor-
+tex, however, a zone of meristematic tissue is found, in which new
+bundles are formed as well as new ground-tissue. In such forms
+the growth is chiefly due to this zone of quiescent tissue.
+
+In the arborescent Monocotyledons, like the Palms and Yuccas,
+the leaves often persist for several years, and when they drop off,
+they may leave behind them traces of their presence on the Corma and
+Royal Palm (Oreodoxa), the base of the leaf forms sheaths about
+the apex of the stem, these shears form clean rings surrounding the
+trunk at regular intervals.
+
+Climbing Stems.--Growing stems are comparatively rare among
+Monocotyledons. Various tropical Araceae (Philodendron, Pothos,
+etc.), Smilax, some species of Asparagus, Dioscorea, Vanilla, are exceptions to the rule.
+
+Branching.--The branching of the stem is almost always mono-
+podial, and the branches arise in the axils of the leaves. A dichoto-
+my of the apex probably takes place in the peculiar "Dom-palm"
+
+376
+BOTANY
+
+(Hyphene Thebaica), of Upper Egypt, and perhaps Pandanus, but this has not been critically investigated.
+
+The Leaf
+
+The leaves of Monocotyledons are usually simple in form, the commonest type being the lanceolate or linear-attenuate leaf, with entire margin. The leaf may have a definite midrib, but often the parallel veins are all alike. A petiole is sometimes present, as in the Palms and Araceae; and in these the leaves may be of great size. True compound leaves occur in some Araceae (e.g. Arisaema).
+
+![]() A
+![]() B
+![]() C
+![]() D
+
+Fig. 347. - A, Agave Americana, cross-section of leaf (× 8); B, section through base of leaf (× 300); C, Phytolacca decandra, stem with four accessory cells (× 300); D, Iriya zephyra, cross-section of stem (× 4); E, Eichhornia crassipes, stem with two accessory cells (× 600).
+
+The apparently compound leaves of Palms owe their pinnae-like form to a tearing into strips of the originally entire lamina.
+
+The attachment of the leaf-base may be narrow, but it is common to find it much expanded, and often developed into a large sheath, which envelops the internodes of the stem. Such sheaths are especially conspicuous in the Grasses and Sedges (Fig. 358, C), and in many aquatic forms like the Pondweed (Potamogeton) and Palm. Free stipules are never found. In most aquatic Monocotyledons, between the sheaths are found membranous axillary scales, which sometimes resemble stipules. Sometimes paired outgrowths (ligules) arise from the junction of the sheath and the base of the lamina (Fig. 358, C).
+
+ANGIOSPERME. 377
+
+**Venation.** — Besides the simple parallel venation usually found, there is sometimes a true reticulate venation, such as that of the Dioscoreaceae, and rarely a reticulate venation is found in many Araceae (e.g. Anthurium, Symplocarpus), in Similax, Dioscorea, *Lilium cordifolium*, and others. In the Scitamineae (e.g. Canna, Maranta, Musa, etc.) the very large leaves have a strong central midrib, with lateral parallel veins radiating from it. The veins of the *Cordycephalaceae* (Cordyceps, *Cordyceps*) are somewhat intermediate in character, the radiating parallel veins being connected by lateral ones. The leaves are usually smooth, with a shining surface, or covered with a waxy bloom (e.g. Agave, *Agave*). In the *Bromeliaceae* (Bromelia), and in the epiphytic Bromelioideae there are formed peculiar epidermal scales, which collect moisture as it falls upon the leaves.
+
+**Histology of the Leaf.**
+
+In upright leaves, leaves such as those of many Liliaceae, the downwardly characteristic of the leaf-surface is not developed. The epidermis is alike upon both sides, and stomata are equally developed. No palisade-parenchyma is present, and the mesophyll is uniform throughout. Where the leaves are broad and flat, as in the *Amaryllidaceae*, the epidermis is thickened on one side only, that of Dioscorea, and the stomata are more abundant upon the lower side. In *Zamioculcas* (Fig. 368) there is a layer of thin-walled cells between the thichk walls, and a layer of thin-walled hypodermal cells lies between the compact palisade-parenchyma and the epidermis. The epidermal cells (Fig. 367, B) are usually surrounded by cells with undulate walls, and in many cases accessory cells are developed around the stomata. These are very marked in *Canna* and in other forms like Canna and Tradescantia.
+
+**Scale-leaves.** — Scale-leaves are developed in many bulbs, and upon the stems of such saprophytes as *Corallorhiza* or *Cephalanthera*, and in similar forms where the foliage leaves are replaced by phylloclades or bracts.
+
+Bracts occur in connection with the inflorescence, and may be very conspicuous. Some of these are the spathe of many Araceae and the brilliantly colored bracts of many Bromeliaceae (Tillandsia, Bilbergia) and Scitamineae (Heliconia, Zingiber).
+
+![]() Fig. 368.—Zamioculcas polystachya. Longitudinal section through a leaf: p., perithium; d., darmanagenes; ost., caryopterous scales.
+
+378
+BOTANY
+
+The Root
+
+The primary or tap-root of the Monocotyledons never persists, and the roots never show a secondary thickening, although in the Palms and Pandanaceae they may be several centimetres in diameter. Aerial roots are common among tropical forms, like the epiphytic Orchids and Araceae, and some members of the Pandanaeae. In the latter they may originate upon the trunk far above the surface of the ground, or even from the branches.
+
+![]() Fig. 360. — Phalaris Canariensis, cross-section of the vascular cylinder of the primary seedling root (× 50). en, endodermis; x, xylem; ph, phloem; p, pericycle; en, endodermis.
+
+The typical root (Fig. 361) shows three layers of cells: an outer layer of narrow,
+plerome, periblem, and calyptrogen, but there may also be a distinct dermatogen. The root-cap is well developed. The aerial root is often formed as an extremity of a spongy body, which is of importance in absorbing moisture. It is wanting in Corallorhiza, where they are replaced by haustoria. This is absent in Corallorhiza, where they are replaced by haustoria. This is probably true of other similar forms. In these there is a mycotrichia or endophytic fungus present, which is of importance in the nutri-
+tion of these forms.
+
+The Flower
+
+![]() Fig. 360. — A, Colchocactus Intus, var. oculatus. B-E, C. nevadensis. B, stamen (× 2). C, cross-section of young capsule (× 2). D, cross-section of young capsule (× 2).
+
+In the simplest flowers, like those of Naias, or some Araceae (Fig. 352), the flower may be reduced to a single carpel or stamen.
+In many of these forms the ovule is terminal, i.e. derived from
+
+ANGIOSPERM.E 379
+
+the floral axis, and not from the carpel, and this is probably the primitive condition among the Angiosperms.
+
+These flowers are usually very crowded into heads or spikes, as in Sparangium, Typha, the Araceae, etc., and are either destitute of any floral envelopes or these are in conspicuous scales.
+
+A somewhat higher type of flower is found in the Alismaeae (Sagittaria, Calla, etc.), which have a perianth (Fig. 350), either didynamous or hermaphrodite, but are furnished with showy petals. The carpels, as well as the other floral leaves, are entirely separate. These apocarps show marked resemblance to some of the lower families of Dicotyledons, notably the Liliaceae, Araceae, and Nymphaeaceae, which may be related to them. The latter family, indeed, has recently been referred to the Monocotyledons.
+
+The majority of the Monocotyledons have the parts of the flower united in one unit, and the flower is usually composed of whorls of three leaves (Fig. 351). In some cases the carpels are united into a compound pistil, the ovary being divided into three chambers (Fig. 352). The ovary is a single cavity, with three placentae bearing the ovules upon its wall (Figs. 350, 351). In the simpler types (e.g. Lilium, Muscari) each whorl of leaf is a monanthus composed of two whorls of entirely free leaves, the outer ones somewhat smaller and sometimes green, two sets of three stamens, and three coherent carpels. When all the parts of the flower are fused and inserted below the perianth they form a monopetalous flower.
+
+In the Amaryllis family (Fig. 368), to which belong the Narcissus, Crinum, etc., the same arrangement of parts is found, but the peri- anth leaves are coherent, and form a tubular perianth, whose base is coherent with the ovary, which thus lies apparently below the outer part of the flower. Flowers with an "in-furrow" ovary are called "Epigynous."
+
+![]() A: Flower diagram showing perianth and sepals.
+B: Bud with sepals.
+C: Pistil with ovary.
+D: Diagram showing ovule formation.
+Fig. 351. — Euphorbia Americanaeum. A, flower and leaves. B, bud (x 4). C, pistil (x 1).
+D, plan of the flower.
+
+800
+BOTANY
+
+In the Iridaceae (Iris, Gladiolus, Sisyrinchium, etc.) the flower (Figs. 353, 369) is much like that of the Amaryllidaceae, but the stamens are reduced to a single whorl on the tube. Some species are otherwise specialized, the single whorl form of the flower in Iris being associated with pollination by special insects, and the same is true of the zygomorphic flowers of Gladiolus.
+
+The most highly specialized monocotyledonous flowers are found in the Solanaceae and Orchidaceae. In China (Fig. 372) the epigynous
+
+![]() A diagram showing a flower with a central column and two lateral columns.
+
+![]() B diagram showing a flower with a central column and two lateral columns.
+
+![]() C diagram showing a flower with a central column and two lateral columns.
+
+![]() D diagram showing a flower with a central column and two lateral columns.
+
+![]() E diagram showing a flower with a central column and two lateral columns.
+
+![]() F diagram showing a flower with a central column and two lateral columns.
+
+![]() G diagram showing a flower with a central column and two lateral columns.
+
+![]() H diagram showing a flower with a central column and two lateral columns.
+
+![]() I diagram showing a flower with a central column and two lateral columns.
+
+![]() J diagram showing a flower with a central column and two lateral columns.
+
+![]() K diagram showing a flower with a central column and two lateral columns.
+
+![]() L diagram showing a flower with a central column and two lateral columns.
+
+![]() M diagram showing a flower with a central column and two lateral columns.
+
+![]() N diagram showing a flower with a central column and two lateral columns.
+
+![]() O diagram showing a flower with a central column and two lateral columns.
+
+![]() P diagram showing a flower with a central column and two lateral columns.
+
+![]() Q diagram showing a flower with a central column and two lateral columns.
+
+![]() R diagram showing a flower with a central column and two lateral columns.
+
+![]() S diagram showing a flower with a central column and two lateral columns.
+
+![]() T diagram showing a flower with a central column and two lateral columns.
+
+![]() U diagram showing a flower with a central column and two lateral columns.
+
+![]() V diagram showing a flower with a central column and two lateral columns.
+
+![]() W diagram showing a flower with a central column and two lateral columns.
+
+![]() X diagram showing a flower with a central column and two lateral columns.
+
+![]() Y diagram showing a flower with a central column and two lateral columns.
+
+![]() Z diagram showing a flower with a central column and two lateral columns.
+
+**Fig. 363.** —A-C, *Arisaema triphyllum.* **A,** inflorescence, the spike cut away as at B; **B,** the single whorl of flowers; **C,** 1st. pistillate flower cut longitudinally. **D,** Loxostylis minor, pistillate flowers cut longitudinally. **E,** Loxostylis major, pistillate flowers cut longitudinally. **F,** *Erythronium dens-canis* (L.) Schott., the stamens of this plant are all present, but only one is fertile, the others being changed to petal-like "Sta- mella," as in the conspicuous part of the flower.
+
+In the Orchidaceae the stamens are reduced to a single one in most cases, and this is united with the upper part of the pistil into the peculiar "lip" (Fig. 374). The flowers are strongly zygomorphic, and with few excep- tions they are absolutely dependent upon insects for pollination.
+
+The flowers of the Monocotyledons may be borne singly, as in some species of Narcissus and Tulip, but more commonly they are in inflo- rescences. The flowers of some species are of enormous size, as in the Century-plant (*Agave Americana*), and many Palma, Yucca, etc.
+
+**Fig. 365.** —A, solanaceous flower of *Strychnos nux-vomica.* **A,** inferior ovary.
+
+**Fig. 366.** —A, zygomorphic flower of *Sisyrinchium bialowae.* **A,** inferior ovary.
+
+**Fig. 367.** —A, zygomorphic flowers of *Gladiolus.* **A,** inferior ovary.
+
+**Fig. 368.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 369.** —A, zygomorphic flowers of *Iris.* **A,** inferior ovary.
+
+**Fig. 370.** —A, zygomorphic flowers of *Gladiolus.* **A,** inferior ovary.
+
+**Fig. 371.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 372.** —A, zygomorphic flowers of *Iris.* **A,** inferior ovary.
+
+**Fig. 373.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 374.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 375.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 376.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 377.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 378.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 379.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 380.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 381.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 382.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 383.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 384.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 385.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 386.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 387.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 388.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 389.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 390.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 391.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 392.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 393.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 394.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 395.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 396.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 397.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 398.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 399.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+**Fig. 400.** —A, zygomorphic flowers of *Orchis.* **A,** inferior ovary.
+
+401
+402
+403
+404
+405
+406
+407
+408
+409
+410
+411
+412
+413
+414
+415
+416
+417
+418
+419
+420
+421
+422
+423
+424
+425
+426
+427
+428
+429
+430
+431
+432
+433
+434
+435
+436
+437
+438
+439
+440381
+
+The Fruit
+
+The fruit of the Monocotyledons may be a dry capsule (Lilium), or achene (Sagittaria), or caryopsis (most Grasses), or it may be a pulpy berry (Asparagus, Smilacina, most Araceae), or a stone-fruit like the Date, Coconut, and other Palms. Pseudo-fruits occur in some, such as the Pineapple, where the edible part of the fruit is derived from the enlarged floral axis and perianth.
+
+Classification of Monocotyledons
+
+The Monocotyledons may be divided into the following orders:
+
+Order I. Helobiose (Flaviales).
+
+Order II. Poaceae.
+
+Order III. Glumiflorae.
+
+Order IV. Principes.
+
+Order V. Symanthae.
+
+Order VI. Liliiflorae.
+
+Order VII. Liliiflorae.
+
+Order VIII. Farinaceae.
+
+Order IX. Scutamineae.
+
+Order X. Silvipermae.
+
+![]() A
+A
+
+![]() B
+B
+
+![]() C
+C
+
+![]() D
+D
+
+![]() E
+E
+
+Fig. 364. — A. Zanztchellia palustris.
+Section of a flower surrounded by a calyx of four scales (X 40). B. E. Passaconopter sp. B.
+Section of a flower with three sepals and a single flower, enlarged. D. The same,
+with the four scales removed to show the stamens and pistil, which is a short
+ripe fruit.
+A third type is shown in Fig. 365. Trig.
+glochin, Alliums, etc., where the short stem is rooted in the mud, and sends up the leaves and flowers above the surface of the shallow water in which they usually grow.
+
+The leaves are linear, with broad sheathing base and axillary scales in the complete flower (Fig. 364). In the genus Zanztchellia, Zanztchellia palustris,
+and Triglochin, with broad lamina and long petiole in Linnomocharis, Alliums, and Sagittaria. In the latter forms the leaves are often reticulately veined, suggest-
+ing certain of the Dioscoreales, with which these forms have other points in common.
+
+381
+
+382
+BOTANY
+
+The flowers in these aquatic forms are very simple, and there are large air-spaces developed, as is always the case in plants having an aquatic habit.
+
+The simplest flowers are found in the Naiadaceae and Lilae. The flowers here may consist of a single stamen or carpel, in both cases developed as the sporophylls of a monopetalous flower (Fig. 350). In the former case the stamens are more or less completely united into a compound pistil. The most
+
+![]() A young inflorescence with pistillate flower (× 1), B, section of gymnoecium, enlarged. C, ripe fruit, enlarged. D, staminate flower (× 1). E, stigma stamen enlarged. F, leaf (× 4). G-I, Rhodos Condones. G, flower, staminate. H, flower, pistillate. I, fruit. J-L, Valliternia spiralis. J, male inflorescence, flowers enclosed in the spathe. K, open spathe, female, stamen enlarged. L, female flower (closed spathe); gy., lobes of the stigma.
+
+Fig. 350.--A-F, Valliternia variabilis. A, young inflorescence with pistillate flower (× 1). B, section of gymnoecium, enlarged. C, ripe fruit, enlarged. D, staminate flower (× 1). E, stigma stamen enlarged. F, leaf (× 4). G-I, Rhodos Condones. G, flower, staminate. H, flower, pistillate. I, fruit. J-L, Valliternia spiralis. J, male inflorescence, flowers enclosed in the spathe. K, open spathe, female, stamen enlarged. L, female flower (closed spathe); gy., lobes of the stigma.
+
+Aberrant forms are found in the Hydrocharitaceae, which perhaps should not be included in this group on account of their being too specialized for the lowly nature of Valliternia and Elodes; they are represented by common species in the Eastern United States. The female flower in these (Fig. 355) has a large inferior ovary, and is borne at the base of a long pedicel; the male flowers are pendulous for pollination, and in Valliternia coils up afterward, drawing the young fruit under water, where it completes its growth.
+
+All these plants belong to the Helobiums. Zostera and Phyllospadix are the principal American genera.
+
+All the other genera belonging to the Helobiums are cosmopolitan; but those belonging to the Naiadaceae and Lilae are confined to North America and Europe.
+
+The flowers of these plants are usually small and inconspicuous; but in some cases they have become highly modified for aquatic life.
+
+In the Naiadaceae and Lilae we find two distinct groups of plants--the Naiadaceae proper and the Lilaceae--which differ from each other in several respects.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens or carpels united into a compound pistil.
+
+The Naiadaceae proper include all those plants which have a single stamen or carpel; while in the Lilaceae there are two or more stamens或
+
+ANGIOSPERME 383
+
+The fruit in all of the Heliochales, except the Hydrocharitaceae, is a nutlet, or a dry or fleshy drupe-like scheme (Potamogeton). In Vallinaria and Elodea it is a leathery, elongated pod, containing a gelatinous substance, which finally bursts open at maturity.
+
+The Heliochales are divided into the following families: Naiafascae, Potamogeto-
+naceae, Lilianaceae, Jungermannaceae, Apono-
+genaceae, Alismaceae, Hydrocharitaceae.
+
+Order II. Pandanales
+
+The Pandanales comprise only a few forms, which are to be considered as primitive types. Some of them, like Typhaeae and Spar-
+ganium, are simple aquatic plants,
+
+![]() A diagram showing parts of a plant.
+Fig. 306. — *Spargangium europarum.* A, part of inflorescence, with pistillate flowers, enlarged; B, single staminate flower, enlarged; C, single pistillate flower, enlarged; D, fruit, enlarged. E, section of the fruit (nutlet) contain-
+ing the seed.
+
+while others, the Screw-pines (Pan-
+danoaceae) are among the largest members of the group.
+
+Classification of Pandanales
+
+The Pandanales are divided into the following families: Typhaeae, Sparganiaceae, and Pandanaceae.
+
+*Fam. 1. Typhaeae.* The Typhaeae are represented by the single genus Typha, the common Cat-tail. These are considered to be the simplest members
+
+![]() A diagram showing a Typha plant.
+Fig. 307. — *Typha glomerata* (× 4).
+(After RAEVY.)
+
+383
+
+884
+BOTANY
+
+of the order. The flat, two-ranked leaves and slender scapes arise from a rhizome. The plicate flowers are crowded together at the lower part of the thick spike, the staminate flowers being at the apex, later falling away from the axis, while the pistillate flowers remain on the spike.
+
+**Fam. 2. Spartaniaceae.** — This family also consists of a single genus, Spar-
+tanum, which is represented by only one species, S. officinale, a native of the southern states of the Eastern United States. S. grevillei, a similar species, occurs in California, and several other species occur within our territory. The flowers are numerous and sessile, and are situated below the scapulae (Fig. 563). The flowers have a rudimentary perianth.
+
+**Fam. 3. Pandanaceae.** — The Pandanus, or Screw-pine, are tropical plants of great beauty and value to man. They are allied to the Pandanus, and they have been placed next these, although they are sometimes supposed to be nearer the Palmae. There are two genera of this family, Pandanus and Pseudophoenix, both of which grow in tropical regions, and Pandanus, mostly arborescent forms of wider distribution than Phoenix, is found in all the Hawaiian tropics. A single species of each genus is found in the Hawaiian Islands.
+
+They are characterized by narrow leaves, arranged upon the stem in a spiral series, hence the name "Screw-pine." The secondary increase in thick-
+ness like that of Yucca or Ira-
+nian date palm. The aerial roots are very characteristic, and the ripe fruit-clusters in some species look like a pine-apple.
+
+Order III. Glumiflorae
+
+The Glumiflorae include the Grasses (Graminae), Sedges (Cyperinae), which are probably not closely related. The Grasses (Graminae) are destitute of a proper perianth, and have only two special chaffy bracts (glumes), which give name to the order.
+
+I. The glume-bearing flowers are usually hermaphrodite, but may be diclinous, as in Indica-
+tum (Fig. 564). A spikelet is a group of the Grasses (Fig. 565) has a single carpel, with a single ovule and two glumes (sometimes two). Less often (Ram-
+busta) there are six stamens, and in some cases (Lolium) there are three more.
+There are usually two plumose styles, which may be joined together, as in the Indian-corn, where each thread of the "silk" is composed of two united styli.
+
+The flowers of the Grasses are arranged in "spikelets," which are enclosed by two glumes, each flower of a spikelet consisting of two bracts ("Pales").
+
+![]() A B C
+
+Fig. 563. *Pandanus macranthus.* A. spikelet, showing leaves; b. large leaf; c. small leaf; d. single flower, showing bracteole; e. and f. the stigmae; st., stem with sheath-like base; lod., lodicules.
+A
+B
+C
+
+ANGIOSPERME. 585
+
+surrounding the sporophyte. The inner palae belong to the floral axis, while the outer palae (or "covering" palaes) surround the inner palae. In the Sedges the outer palae there are usually present two small basal (or "spines"), which, by their enlargement, force open the palaes. These are sometimes considered to be rudiments of the sepals, but there is much doubt about this.
+
+In the Sedges (Fig. 300) the flowers are more commonly distinguished from those of the Grasses, but structurally are similar to them.
+
+The fruit is indehiscent, a nutlet or Caryopsis, and the abundance of seeds in many Grasses makes these the most important of all food plants. The seed of the Grasses consists of the Caryopsis, which is closely adherent to the ovary. The embryo in the ripe grain is enclosed in a coat, the Graminae, and the only one (Sorghum), acts as an absorber organ for the liquid in the grain. In the Sedges the embryo is at the apex of the endosperm (Fig. 301). The embryo has developed than it is in the Grasses.
+
+The Grasses and Sedges are widespread, especially important to man throughout the world. The Sedges are largely water-plants, but the Grasses often grow on land in various regions, where they are the most important plants, as upon our own soil in Europe. All members of the group have jointed stems and long sheathing leaves. The leaves are narrow and split sheaths, in the Graminae, three-lobed sheaths, in the Sedges. The stems are usually hollow in the Graminae, and solid in the Sedges. The giants of the order are the Bamboos, some of which are 30 to 40 metres in height. The outer tissues of all of them are hollow.
+
+Economically the Sedges are of small importance. Perhaps the most noteworthy of these is the Papyrus (Cyperus papyrus). The Graminae, on the other hand, are very important as food for man and animals. They form almost the staple food of herbivorous animals, and all the cereals--Wheat, Rice, Corn, etc., are Grasses. The Bamboo and Sugar-cane are also Grasses. Of our native Grasses, the Wild-rice (Zizania aquatica) is the most important as a source of food.
+
+2
+
+385
+BOTANY
+
+Order IV. Principes (Palmae)
+
+The Palmae constitute an extremely natural order. While they are mainly tropical forms, several species extend into the warm-temperate zones. In the Atlantic States, the genus *Caryota* occurs, and several species of *Livistona* and Southern California are found species of *Washingtonia* (Pritchardia) and *Rhytispha*. All of these are Fan-palms.
+
+Some of the smaller Palms do not develop an erect stem, but in most of them the stem forms a columnar trunk, sometimes fifty metres in height. In spite of
+
+![]()
+A - C. *Caryota* plant with malecat. A, pollinaria. B, inflorescence.
+B, staminate flower, enlarged. C, female flower. D, fruit of *C. umbraculifera*.
+(× 1). E, single fruit, slightly enlarged. F, akene, removed from the involucre.
+G, second fruit, akene; en., embryo. H, *Scorpio* incertus. I, single malecat.
+J, flower, enlarged.
+
+
+Fig. 300.
+
+Its size, its structure does not differ essentially from that of the typical mono-
+cotyledonous stem, and the same is true of the roots, which are produced in great numbers, sometimes from a distance above the ground.
+
+The form of the trunk is usually cylindrical; but when the crown of leaves has reached nearly its full size. Branching of the trunk, apparently a true dichoto-
+my, occurs in the "Doom-palm" (*Hyphaene* of Upper Egypt), but is absent in other forms. The "Cane-palm" (*Phoenicophyllum*) is a monopodial stem at the base of the stem (*Phoenix Canariensis*). In the Rattan-palms (*Calamus*)
+
+The following genera are included in this order:
+
+**Caryota** (Figs. 300-302).
+
+386
+
+. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
+
+PLATE VI
+
+Coconut Palms, Brazil. (Photograph by Dr. J. C. Branner.)
+
+ANGIOSPERM.E 387
+
+the extremely slender stem reaches a great length, and climbs by means of hooks developed upon the scattered leaves.
+
+The leaves are usually young, and split more or less com-
+pletely along the lines of these folds. Two types of leaves occur, the fan-
+shaped (Caryota, Phoenix, Areca), and the palmate (Cocos, Cocos-octa,
+Cocos, Orecocoxa, etc.). Bipinnate leaves are found in Caryota. The leaves may remain attached for a long time, and the trunk then is rough with the alternate leaf scars. When the plant is old, and the leaves have fallen off (repi.), the leaves fall off, leaving a smooth scar encircling the trunk below the base of the next younger leaf.
+
+The flowers of Palms (Fig. 361) are simple in structure, and may be hermaphrodite (Sabah) or ditelous (Phoenix); in the latter genus they are dioecious, but most Palms are monoecious. A perianth of three to six leaves is generally present, and there are from six to many stamens. The carpels are
+
+![]() A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
+
+Fig. 361.—A-E, Phoenix Canariensis; F, two plicate flowers which have been formed; G, two of the three carpels, car, are abortive; C, a similar flower, seen from in front, showing the single fertile carpel; and two sterile carpels; D, a similar flower, seen from behind; E, a single fertile carpel; F, a pistil; G, fruit; H, single flower (× 1); I, fruit (× 1). Gt., the plinth.
+
+always three and may be separate or united. In the latter case, not infrequently by a single one meiosis.
+
+The flowers are borne in large inflorescences, often extensively branched, and of gigantic size. In a few instances, like the Talipot-palm (Corypha Talieira), they are the only after-fruiting organs.
+
+In other Palms the inflorescence arises as a lateral branch, and is surrounded while young by a sheath-like bract.
+
+The fruit is usually a berry, or scone-fruit, which may reach great size (Co-
+coe). The edible fruits of many Palms, as well as the value of the Palms in furnishing shade and shelter for human beings and animals is due to all plants. Besides the fruit, other parts of the tree, the young shoots, the fermented sap, and the pith (Nag-palm), are important articles of food.
+Dietrichia (Dietrichia palustris) is found in swamps in Southern California; it is inhabitants of arid regions; but it is in the moist forests of the Tropics that they reach their greatest development. Here they become stately trees with leaves of gigantic size. Some species of Areca and Caryota have
+
+388
+BOTANY
+
+pinnae leaves, ten to fifteen metres in length, and the fan-shaped leaves of *Corypha umbraculifera* are four to five metres in diameter.
+
+**Order V. *Synanthae***
+
+The order *Synanthae* comprises a single family of palm-like plants, the *Caryothraceae*. They are confined to the American Tropics, and in appearance closely resemble small Fan-palms (Fig. 362). The flowers, however, are more numerous than those of the Fan-palm.
+
+From the leaves of species of *Cardiovista* are manu-
+factured the famous Fan-
+palm hats.
+
+**Order VI. *Spathifera***
+
+The Spathifera include two families, the Araceae, of which many genera number belong, and the Lomariopsidae.
+
+Fam. I. *Araceae.* — The Araceae are principally tropical plants, but a small number of genera (*Acorus*, Calia, Symplo-
+carpus, *Calathea*) occur in temperate regions as well. The latter are like the familiar "Calathea" (Ricardia), and various species of *Calathus-
+rium and Caladium, are cultivated for their fine foliage and flower-sen-
+sences. The latter owe their beauty to the large
+leaf (Fig. 363) that sur-
+rounds the flowers (Fig.
+364).
+
+Fig. 362. — *Cardiavista palmae.* (After Ranz.) — The leaves of this plant are borne upon a thick spike,
+or Spadix. In *Spathiphyllum* (Fig. 365) the spadix and spathe are completely coherent; the spathe is greenish-yellow, and the spadix is a berry, which is often brilliantly colored (e.g. *Araceae tripartita*). The embryo may fill the seed (Lycisicum) or there may be endosperm present (*Philodendron*).
+
+The leaves of the Araceae are usually simple or com-
+pound. The venation may be parallel (*Richiardia*), but more often it is reticu-
+late. The Araceae are represented in many tropical forests by many striking forms such as *Dioncophyllum*, of Central America; some terre-
+trial plants with giant leaves; others, like Philodendron, and species of Anthu-
+
+ANGIOSPERM. E 300
+
+rium, are climbers, reaching to the tops of trees, and are among the most characteristic of all plants. *Monstera deliciosa*, with its big perforate leaves, is familiar to every one.
+
+The flowers of the Araceae show a good deal of variety. In the simplest forms, e.g. *Aglaiocoma*, Spathicarpa, the flowers consist of a single calyx, with a basal ovule, of which the stamens are usually wanting. In *Corymbium* (Fig. 356), the compound ovary, and the flowers are hermaphrodite, with a rudimentary perianth. The flowers may be connected to the base of the spathe (Araceae), or they may be attached to the tip (Spathicarpa). In *Annona* (Syzygium), the spathe reaches an enormous size. In *Amorphophallus titanum*, the spathe is nearly a meter in length, and is so large that it is difficult to see through it. The temperature is very marked, and a thermometer thrust into the spathe, especially at the time that the pollen is being shed, indicates a much higher temperature than that of the surrounding atmosphere. In *Philodendron macrocarpum*, an East Indian species, Kraus found a maximum difference of 12.8° C. This took place in the evening, and was accompanied by an increase in the odor, which is often very pronounced in these plants. The flowers are hermaphrodite, and are attached to the spathe, and thus receive the pollen, which they afterward carry to another inflorescence.
+
+Such forms attract carrion-insects, which serve to pollinate them.
+
+**Epidogy:** The flowers of many Araceae are visited by numerous needle-shaped insects, or saprophages, to which has been attributed the extremely acrid taste of many of them. Some of them (*Dregeanthes segrini*) possess a milky juice, which is used as a medicine.
+
+**Fam. 1. Lomaceae.** — The very much reduced plants, the Lomaceae (Fig.
+356), are related to the Araceae, and are sometimes included with them. *Lema* has roots; *Wolffia* is a weed. The latter is the smallest of all vascular plants,
+
+![]() A simple diagram showing three different types of Araceae flowers: A) A single flower with a central ovule and no visible stamens; B) A flower with a compound ovary and no visible stamens; C) A flower with a central ovary and visible stamens.
+![]() D) A flower with a central ovary and visible stamens.
+
+Fig. 356.—A. Spathicarpa aquifolia, the simple flowers attached to the half-like spathe, on p. 171; B. *Aglaiocoma*. I. and piliacea; II. flowers, enlarged; C. leaf of *Ardisia triphylla* (x 1); D. *Nephrophyta Liberica*, fruits (x 1).
+
+300
+
+300
+BOTANY
+
+being a little oval body a millimetre or so in diameter. Two species occur in the Eastern United States. The flowers in the Liliaceae consist of a single corolla or stamen, the flowers being grouped in a small inflorescence.
+
+Order VII. Liliifera
+
+The Liliifera are often considered to be the "typical" Monocotyledons, and comprise many of the most familiar and showy flowers both wild and cultivated.
+With few exceptions the flowers show the typical arrangement, i.e.
+two whorls of perianth leaves (Fig. 360). The two whorls of perianth leaves may be alike, or occasionally one may be green (Trillium). Within the order are included the radially symmetrical, hypogynous flowers of the true Lilies, and the radially symmetrical, epigynous flowers of many Iridaceae. The fruit is usually a dry, trilocular capsule, but it may be a berry, such as in the Agave, or Citonia. The embryo is small, rarely more than 1 mm long.
+
+The Liliifera are, for the most part, perennial herbaceous plants, with terminal or axillary annual flowering shoots. In the warmer parts of the world they may become woody. They are found throughout the Southwestern States, and the Inca-
+ceae and Compositae of the Old World.
+In some countries (e.g., South Africa,
+Dioscorea, Bryonia) are climbers.
+Among the most common Liliifera
+are the Juncaceae, Liliaceae, Amaryllidaceae, Iridaceae, Diosco-
+ceae, Tacsonia, and the Orchideae.
+
+Fam. 1. Juncaceae — The Rushes
+(Fig. 361), a family of perennial plants,
+resembling in their floral structure those of the Compositae. The leaves are reduced to scales or filaments.
+times considered to be degraded Lililaceae, but now placed in a separate family.
+
+Fam. 2. Liliaceae — This is the largest family of the order, and includes many of the most beautiful of all flowers. They are especially well developed in many parts of Europe and North America, and California. The true Lilies (Lilium), Tulip, Hyacinth, Erythronium, Trillium, are familiar examples. Among the characteristic western genera may be men-
+tioned Calochortus (Fig. 360), Reddies (Fig. 360), Frasillaria, and Yucca.
+
+![]() Fig. 360 — Anthurum festoidi.
+Flowers of Anthurum festoidi.
+
+. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
+
+PLATE VII
+
+Yucca arborescens, growing in the Mojave Desert of Southern California.
+(Photograph by Prof. W. Trelease.)
+
+![]() A black-and-white photograph of a Joshua tree (Yucca brevifolia) growing in a desert landscape. The tree has a tall trunk with large, spiky leaves at the top. The surrounding ground is covered with sparse vegetation.
+
+ANGIOSPERM.AE
+391
+
+**Fam. 3. Amaryllidaceae.** — The Amaryllidaceae differ from the Liliaceae in having an inferior ovary, and sometimes zygomorphic flowers. Very few of these grow within our territory. The Agave (Agave americana), with its large, showy, yellowish-white, or purple
+anthos ("Atamasco-illy"), and
+Hyacinthus orientalis, with its
+most important. A number of com-
+mon garden flowers—Galanthus,
+ Narcissus, Amaryllis—belong to this family.
+
+**Fam. 4. Iridaceae.** — The Iridaceae have zygomorphic flowers.
+Amaryllidaceae, from which they dif-
+fer in having the stamens reduced
+to three, and the petals opposite the
+flowers, with the segments all alike
+(Synonym: "Iris"). The sepals or
+segments (petals) may be different
+from the outer ones, as in Iris (Fig.
+300) and Gladiolus (Fig. 301).
+(Gladiolus, Freesia, the flowers are
+markedly zygomorphic.)
+
+The Iridaceae are especially abun-
+dant in the Cape region of Africa,
+where many beautiful forms of
+these are introduced. Gladiolus, Iris,
+Freesia, Sparaxis, are among
+the most striking of these.
+
+The leaves of the Iridaceae are sharply folded longitudinally, and the leafy shoots with their two-ranked leaves are thus strongly flattened. Such leaves are termed "Equitant."
+
+**Fam. 5. Dioscoreaceae.** — The Dioscoreaceae, or Yam family, include a num-
+ber of twining, mostly tropical, plants with heart-shaped, reticulate-veined leaves, and inconspicuous, mostly didynamous flowers, the pellate flowers with
+
+![]() A
+![]() B
+![]() C
+![]() D
+![]() E
+![]() F
+![]() G
+![]() H
+
+**Fig. 300. — A, B. *Iris tricolor*. Plant, showing method of budding. B-D. *Iris*. Two plants (x 8); r, root; f, flowers.
+E. section of female flower.
+
+**Fig. 301. — A, B. *Gladiolus capitatus*. A, inflorescence (x 1). B, flower opened to show arrangement of parts. C, flower of B. Incor-
+porated into the text as a figure reference for further discussion on the topic of Iridaceae and their characteristics.
+
+306
+BOTANY
+
+Indoor crass. A single species (Dioscorea villosa) is common in the eastern United States. *D. lotus* is the common Yam.
+
+Fam. 6. Taccaceae, Hammodoraceae. -- The Taccaceae and Hammodoraceae are small families without any common representatives.
+
+Order VIII. Farinaceae
+
+The Farinaceae comprise several families, some of which are often included with the Liliiflorae. They are distinguished especially by the character of the
+
+![]() A flower with long, thin petals and a central cluster of stamens.
+
+Fig. 307. -- *Hypoxanthum nitidum* (x4). (After HALEY.)
+
+endosperm, which is copious, and mealy in consistence. The ovules are often orthotropous, but rarely anatropous. The flowers are usually large and are largely tropical in their distribution. The most familiar genus is Tradescantia (Fig. 305), belonging to the Commelinaeae. Pontederia and Tillandsia represent the Pontederiaceae and Bromeliaceae respectively. The only American members of these families are Mayacaea, Xyridacea, and Ericoaceae.
+
+Pontederiaceae are usually confined to the tropics.
+
+Pontederia cordata, the Pickerelweed (Fig. 310), is our only common representative. The Water-hyacinth (*Eichhornia crassipes*) is now commonly planted in
+
+ANGIOSPERM. 308
+
+ponds, and at the South has become naturalized, and in some places causes much trouble by the ra-
+pidity with which it has increased. The flowers are strongly zygomorphic, and in *Pentas* and *Bromeliaceae*, are trimerous, i.e. there are three different lengths of stamens and styles.
+
+*Bromeliaceae.* — The Bromeliads are ex-
+tensively American, and espe-
+cially developed in the tropics of Central America,
+and the West Indies. A few species of Tillandsia,
+among them the well-known
+"Spanish-moss" (T. us-
+soides), belong to this
+family in the United States. The flowers, simi-
+larly, are much like those of the true Lilies. They are often in spikes, the flowers being on axis of showy pink or scarlet bracts. With few excep-
+tions they are epiphytes, and are a conspicuous feature among the flora of tropical America. The leaves are long and slender, often crowded together at the base of the plant (Fig. 368). The bases serve as reservoirs of moisture,
+and accumulate, also, dust and humidity. The upper leaves are scurfy scales, which also serve as reservoirs of water. *Ananas* (Ananas suave) is the most familiar member of the family. The fruit, however, is not a flower but a cluster of flowers, attached to the juicy floral axis—the whole structure is much like a pineapple.
+
+The roots in these plants are mainly as organs of attachment, and may be very numerous.
+
+Order IX. Scitamineae.
+
+The Scitamineae are, with very few exceptions, tropical plants, fre-
+
+![]()
+A: A flower.
+B: A flower.
+C: A flower.
+D: A flower.
+E: A flower.
+F: A flower.
+G: A flower.
+H: A flower.
+I: A flower.
+J: A flower.
+K: A flower.
+L: A flower.
+M: A flower.
+N: A flower.
+O: A flower.
+P: A flower.
+Q: A flower.
+R: A flower.
+S: A flower.
+T: A flower.
+U: A flower.
+V: A flower.
+W: A flower.
+X: A flower.
+Y: A flower.
+Z: A flower.
+AA: A flower.
+AB: A flower.
+AC: A flower.
+AD: A flower.
+AE: A flower.
+AF: A flower.
+AG: A flower.
+AH: A flower.
+AI: A flower.
+AJ: A flower.
+AK: A flower.
+AL: A flower.
+AM: A flower.
+AN: A flower.
+AO: A flower.
+AP: A flower.
+AQ: A flower.
+AR: A flower.
+AS: A flower.
+AT: A flower.
+AU: A flower.
+AV: A flower.
+AW: A flower.
+AX: A flower.
+AY: A flower.
+AZ: A flower.
+BA: A flower.
+BB: A flower.
+BC: A flower.
+BD: A flower.
+BE: A flower.
+BF: A flower.
+BG: A flower.
+BH: A flower.
+BI: A flower.
+BJ: A flower.
+BK: A flower.
+BL: A flower.
+BM: A flower.
+BN: A flower.
+BO: A flower.
+BP: A flower.
+BQ: A flower.
+BR: A flower.
+BS: A flower.
+BT: A flower.
+BU: A flower.
+BV: A flower.
+BW: A flower.
+BX: A flower.
+BY: A flower.
+BZ: A flower.
+
+Fig. 368. — *Tillandsia* virginica. Inflorescence, reduced. B, pistil. C, stamen, enlarged, showing the staminodial hairs.
+
+Order IX. Scitamineae.
+
+The Scitamineae are, with very few exceptions, tropical plants, fre-
+
+384
+BOTANY
+
+quantity of large leaves, and extremely characteristic. They have simple leaves, often very large, as in the Banana (Musa). The leaves are rolled up transverse when young and have a strong midrib, from which lateral parallel veins run to the margin. The leaves are usually stalked, and the leaf-base is largely developed, forming a sheath round the stem, which is often thickened. There is commonly an underground stem, or rhizome, from which the aerial shoots are produced. These, with few exceptions, bear a single inflorescence which ends the growth of the shoot.
+
+A
+
+B
+
+C
+
+Fig. 370. *Pseudotria cordata*. A, bud and young flower-bud; B, single flower, showing the two sets of stamens; C, cross-section of ovary, showing fertile and two sterile carpels.
+(Plate 371.) *Bilbergia zeylanica.*
+(After Rauk.)
+
+In the "Traveler's-tree" ("Ravenala") there is a perennial upright trunk, and the inflorescences are lateral. The enlarged leaf-bases of this plant serve as reservoirs for water.
+
+The flowers are symmorphic, and only very rarely are all the stamens developed. The corolla is interior, and the seeds contain a small embryo, which is embedded in a fleshy endospermous mass surrounding the albumen of the ovule. The flowers are often borne in the axis of conspicuous bracts, which sometimes form a panicle. In some species (Hibiscus) the flowers are yellow, or scarlet and yellow, bracts of great beauty; and the fruits of some species of Zingiber are white or pink.
+
+The leaves are large and showy, found in the Musaceae, or Banana family.
+
+Here five perfect stamens are generally present, and a rudiment of the sixth one is often apparent. In the Ginger family (*Zingiberaceae*) only one perfect stamen is developed, each pair of stamens being paired and pedicellate, curiously resembling the labellum of an Orchid (Fig. 572. G).
+
+![]() A diagram showing a flower with five stamens and a single pistil.
+![]() A diagram showing a flower with five stamens and a single pistil.
+![]() A diagram showing a flower with five stamens and a single pistil.
+![]() A diagram showing a flower with five stamens and a single pistil.
+![]() A diagram showing a flower with five stamens and a single pistil.
+
+ANGIOSPERMAE 395
+
+**Cannaceae.** — In the familiar genus *Canna* (Fig. 372), which is the only genus of the Cannaceae, and very common in our gardens, five of the stamens changed into petaloid staminodia, which form the showy part of the flower, the perianth being quite inconspicuous. The sixth stamen is also petaloid, but upon one side is a long, slender appendage, special of *Canna* × *picta*, native in Florida.
+
+**Marantaceae.** — The Marantaceae are principally confined to the American Tropics, and include a number of showy-flowered forms cultivated in greenhouses.
+
+![]() A diagram showing the structure of a flower of *Canna*. It shows the upper part of the flowering shoot, much reduced; B, flower, showing the staminodia, st., and fertile stamen, et.; C, corolla; D, style; E, fertile stamen and pistil; F, section of ovary, enlarged. E nearly ripe capsule with seeds; G, seed; H, embryo; J, perisperm. G. stipule. (After Becc and Schmid.)
+
+The structure of the flowers is much like that of *Canna*. *Maranta arundinacea* furnishes Arrow-wood.
+
+Economically the genus *Musa* holds the first rank among the Solanaceae. The Plantain (*M. paradisiaca*) and Banana (*P. sapientum*) are among the most important of food-plants, and *M. tessile* furnishes Manila hemp.
+
+**Order X. Microsermae**
+
+The Microsermae, the most specialized of the Monocotyledons, are also the most numerous, the number of described species exceeding five thousand. Neverthelessthey are seldom common plants, and in spite of the extraordinary device especially developed for insect-pollination they do not appear to have been remarkably successful in their struggle for existence. There are two suborders:
+
+
+
+ | A |
+ B |
+ C |
+ D |
+ E |
+ F |
+
+
+ | G |
+ H |
+ I |
+ J |
+ K |
+ L |
+
+
+ | et. |
+ car. |
+ car. |
+ car. |
+ car. |
+ car. |
+
+
+ | et. |
+ car. |
+ car. |
+ car. |
+ car. |
+ car. |
+
+
+ | et. |
+ car. |
+ car. |
+ car. |
+ car. |
+ car. |
+
+
+ | et. |
+ car. |
+ car. |
+ car. |
+ car. |
+ car. |
+
+
+ | et. |
+ car. |
+ car. |
+ car. |
+ car. |
+ car. |
+
+
+ | et. |
+ car. |
+ car. |
+ car. |
+ car. |
+ car. |
+
+
+ | et. |
+ car. |
+ car. |
+ car. |
+ car. |
+ car. |
+
+
+ | et. |
+ car. |
+ car. |
+ car. |
+ car. |
+ car. |
+
+
+ | et. |
+ car. |
+ car. |
+ car. |
+ car. |
+ | Fig. 372 - A-F, Canna Indian. A, upper part of flowering shoot, much reduced; B, flower, showing the staminodia, et., and fertile stamen, et.; C, corolla; D, style; E, fertile stamen and pistil; F, section of ovary, enlarged. E nearly ripe capsule with seeds; G, seed; H, embryo; J, perisperm. G. stipule. (After Becc and Schmid.) |
|---|
| |
|---|
|