356 



DICOTYLEDONOUS GERMINATION. 



thus remains within the embryo, and sends out radicles (adventitious 

 or secondary rootlets) from its surface, the plants are said to be endo- 

 rhizal (eydov, within, g/^a, a root). See page 42. 



Dicotyledonous Geemination. — In Dicotyledons, the cotyledons 

 generally separate from the integuments, and either appear above 

 ground in the form of temporary leaves (figs. 627, 628 c c), which 

 differ in form from the permanent leaves of the plant (fig. 628 g), or 

 remain below as fleshy lobes. In the former case they are epigeal (it!, 



Pig. 627. 



Pig. 629. 



upon or above, yea, y\ the earth), in the latter case (as in Beans, 

 Araohis, etc.), they are hyjwgeal (v'tto, under). The cotyledons usually 

 separate, but sometimes they are united, and appear as one. In all 

 cases, the plumule (figs. 627, 628 g) proceeds from between the two 

 cotyledons, a.nd does not pierce through a sheath as in monocotyle- 



Fig. 627. Germination of the dicotyledonous embryo of Acer Neguildo. m, CoUum, 

 collar or neck, r, Root, t, Caulicule or stem, c c, Cotyledons. ^, Gemmule or plumule. 

 Pig. 628. Upper part of tlie same embryo more developed, cc, Cotyledons, g, Gemmule, 

 the first leaves of which are already expanded, i, Caulicule or stem. -Pig. 629. Acotyle- 

 donous embryos or spores of Marchantia polymoi-pha, germinating. 1, Spore in the early 

 stage of germination. 2, In a more advanced stage. The spores are simple cells, which 

 elongate during germination at some point of their surface. They are heterorhizal. They 

 may be compared to naked embryos rather than to seeds. 



