CHAPTEK 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 c:er- 

 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- 

 fore an egg is organ- 

 ized and fertiliza- 

 tion takes place. In 

 both cases endo- 



Fio. 74. — Two modes of initiating the formation of endo- 

 sperm. A, J'aias 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. 2?, Datura laevis, nuclear division 

 followed immediately by formation of wall; x 225.— 

 After Guionard.«. *« 



sperm is formed 



after fertilization; but in Gymnosperms it is a continuation 

 oi cell division, while in Angiosperms it usually begins with 

 nuclear fusion followed bv simultaneous and often free nuclear 



165 



