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- 

 sperms this con- 

 tinues for some 

 time and is re- 

 placed by cell-for- 

 mation, giving rise 

 to an extensive tis- 

 sue bearing arche- 

 gonia, while in An- 

 giosperms usually 

 only eight free nu- 

 clei are formed be- Fig. 74.— Two modes of initiating the formation of endo- 

 f Ore an e ' 0, is Orffan- sperm. A, Naias major, illustrating free nuclear divi- 



™ ,°. sion ; there are four free nuclei belonging to the endo- 



lzeu and iertlliza- sperm, the lower free nucleus being that of the upper 



tion takes place. In antipodal; x 175. B, Datura laevis, nuclear division 



both cases endo- followed immediately by formation of wall ; x 225.— 



■ — t After Guignard.* 2 . 4e 



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 



