DEVELOPMENT OF PLANTS 



363 



divisions of the embryo cell of the pro-embryo, assisted to a 

 varying extent by one or more of the adjoining cells of the sus- 

 pensor (Fig. 275, C-F). The remaining cells of the suspensor 



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 s, suspensor; e, embryo cell; en, endosperm cells. C, pro-embryo 

 after first division of embryo cells. D, further divisions of embryo cell, 

 showing 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. 



are ultimately disorganized or they may increase greatly in size 

 and themselves become the principal means of absorbing food and 

 transferring it to the embryo. The structure of the mature 

 embryo varies greatly. In some genera, as in the orchids, Indian 

 pipe, etc., it remains rudimentary, consisting of only a few cells. 



