DEVELOPMENT OF PLANTS 375 



sporangium. The endosperm nucleus plays a very important 

 role'in the development of the sporophyte, for as soon as fertiliza- 

 tion has been effected it forms by repeated division a mass of cells 

 that completely fills the entire space within the enlarging spore, 

 thus providing food for the nourishment of the sporophyte. At 



Fig. 271. Section of a megasporangium of lily, showing the mature female 

 gametophyte: 9, female gamete, below which are two synergids; p, the 

 two polar nuclei uniting to form the endosperm nucleus; a, antipodal cells; 

 mi, micropyle; i, integuments; /, funiculus in which a vascular bundle, v , 

 has been formed to transport foods to the sporangium. 



first sight it would appear impossible to compare the various cells 

 of this peculiar gametophyte with the tissues of the female gam- 

 etophyte of the gymnosperms or ferns. It has been suggested 

 that the female gamete and the synergids are the remains of three 

 archegonia, only one of which is usually capable of being fertilized. 



