38o 



EMBRYO OF ANGIOSPERMS 



cells is called the endosperm and the method of its development 

 is exactly similar to that of the female gametophyte of the gym- 

 nosperm, and it serves the same purpose, namely, to nourish the 

 young sporophyte or embryo. Recall, however, that it originates 

 in a different manner and at a different time in the life cycle. 



Fig. 275. Stages in the germination of the gametospore of Lepidium, 

 sectional view: A, micropylar end of embryo sac, showing the enlarging 

 gametospore provided with cell wall and attached to wall of sac. B, later 

 growth — 5, suspensor; e, embryo cell; en, endosperm cells. C, pro-embryo 

 after first division of embryo cell. D, further divisions of embryo cell, show- 

 ing formation of an epidermis and a central stem region. E, later growth, 

 two growing regions, the cotyledons, appearing on the sides of the stem. F, 

 micropylar end of the embryo sac in which the embryo cell has formed a small 

 plant or embryo, consisting of two cotyledons, c; stem, st, which terminates 

 in the root, r; the endosperm cells, en, are being absorbed by the enlarging 

 embryo; s, suspensor. 



The germination of the gametospore and the formation of the 

 embryo vary so greatly that only a very general statement can 

 be made. Following fertilization, the gametospore becomes sur- 

 rounded by a cell wall and attached to the wall of the embryo 



