tokens: " Salix purpurea " ) , chopos o álamos ( " Populus tremula , Populus alba , Populus nigra " ) , fresnos ( " Fraxinus angustifolia " ) , olmos ( negrillos ) ( " Ulmus minor " ) , espinos ( " Crataegus monogyna " ) , endrinos ( " Prunus spinosa " ) .