66 



■ORGANOGRAPHY. 



151 



. OMT. group to whicli tliey belong is said 

 to be dicotyledonous (Fig. 1 J9.) 

 Most of the cone-bearing plants 

 {Coniferce) have polycotyled- 

 onous embryos. The nourishment 

 for the plantlet during germina- 

 tion is stored up ■wholly (Pea, 

 Bean, Maple), or in part (Corn, 

 Wheat), in the cotyle- 

 dons. The portion, if 

 any, stored within the 

 embryo-sac, but not in 

 the cotyledons (Fig. 150, 

 en), is called endos- 

 perm (Gr. endon, with- 

 in) ; that, if any, outside 



the embryo-sac is called the perisperm (Gr.peri, around). 

 84. The integuments of the seed correspond with those 



of the ovule, and are called the testa. It often has, to 



assist the dissemination of the seed, outgrowths, in the shape 



of a wing, as in the Pine, Trumpet 



Creeper (Fig. 151) etc., or it may have 



a tuft of hairs, called coma, as the 



Milkweed (Fig. 152) and Epilobium ; 



or a hairy covering, as the Cotton-seeds. 



The testa in many seeds is crustaceous, 



in others it becomes berry-like, and the 



edible pulp causes the seeds to be eaten 



and disseminated by birds. The seed is 



Fig. 150. Section of a monocotyledonous seed (grain of Indian Corn) : cot, coty- 

 ledon : r, radicle ; //, plumule ; en, endosperm. Fig. 151. Winged seed of Trum- 

 pet Creeper {Teconta radicans). Fig. 152. Comose seed of IMilkweed {^Asclepiiis 

 Cornuii). 



