DEVELOPMENT OF PLANTS 



379 



the gametospore. Formerly it was believed that the second 

 male gamete disintegrated, but in recent years numerous in- 

 stances of its fusion with the endosperm nucleus have been ob- 

 served and this mode of formation of the endosperm nucleus 

 through the triple fusion of the two polar cells and one of the 

 male gametes is doubtless the rule. While this process is prob- 

 ably in the nature of a reinforcement, enabling the endosperm 

 nucleus to perform its work, it is noteworthy that the qualities of 

 the male parent are transmitted to the endosperm cell just as 

 though this fusion were a sexual process. 



127. The Germination of the Gametospore. — After fertiliza- 

 tion the endosperm nucleus divides repeatedly, and usually the 



Fig. 274. Sectional view of megasporophylls of Lepidium shortly after 

 fertilization (see Fig. 269): en, early development of endosperm cells about 

 wall of embryo sac; p, young sporophyte developing from gametospore; 

 mi, micropyle; s, stigma;/, funiculus. 



resulting nuclei become arranged about the walls of the sac-like 

 gametophyte which may now be called the embryo sac (Fig. 

 274). Later the endosperm cells develop walls and by further 

 division completely fill the embryo sac with cells. This mass of 



