SPERMATOPIIYTES : ANGIOSPERMS 



205 



The three nuclei at the other end of the sac are also or- 

 ganized into cells, and usually have walls. These cells are 

 known as anti2)odal cells (Fig. 176, at right, 

 B). The large nucleus near the center of A 



the sac, formed by the fusion of the two / \ 



Fig. 176. Lilium Philadelphicum, showing last stages of germination of megaspore 

 before fertilization: the embryo sac to the left contains the pair of nuclei in each 

 end in a state of division preparatory to the stage represented by the middle figure, 

 in which there are four nuclei at each end ; the figure to the right shows an embryo- 

 sac containing a gametopliyte about ready for fertilization, with the egg apparatus 

 {A) composed of the two syncrgids and egg (central and lower), the three antipo- 

 dal cells {B), and the two polar nuclei fusing (C) to form the primary endosperm 

 nucleus.— Caldwkli.. 



polar nuclei, is known as the primari/ endosperm nucleus 

 or the definitive nucleus. 



