CHAPTER VIII 



THE ENDOSPERM 



THE endosperm of Gymnosperms seems to be clearly the 

 vegetative tissue of the female gametophyte, but the morpho- 

 logical nature of the endosperm of Angiosperms (Fig. 74) is not 

 so clear. The ger- 

 mination of the 

 megaspore begins, 

 as in Gymnosperms, 

 with free and simul- 

 taneous nuclear di- 

 vision. In Gymno- 

 this 



sperms 

 tinues 

 time and 

 placed by 



for 



con- 

 some 

 is re- 

 cell-for- 



mation, giving rise 

 to an extensive tis- 

 sue bearing arche- 

 gonia, while in ^i- 

 giosperms usually 

 only eight free nu- 

 clei are formed be- 

 fore an egg is organ- 

 ized and fertiliza- 

 tion takes place. In 

 both cases endo- 

 sperm is formed 

 after fertilization; but in Gymnosperms it is a continuation 

 of cell division, while in Angiosperms it usually begins with 

 nuclear fusion followed by simultaneous and often free nuclear 



165 



A 



FIG. 74. Two modes of initiating the formation of endo- 

 sperm. A, Ifaias major, illustrating free nuclear divi- 

 sion ; there are four free nuclei belonging to the endo- 

 ' sperm, the lower free nucleus being that of the upper 

 antipodal ; x 175. B, Datura, laevis, nuclear division 

 followed immediately by formation of wall ; x 225. 



