SPERMATOPIIYTES: ANGIOSPKUMS 



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 antipodal cells (Fig. 176, at right, 

 B). The large nucleus near the center of 

 the sac, formed by the fusion of the two 



PIG. 176. Liliurn 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 gametophyte about ready for fertilization, with the egg apparatus 

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

 dal cells (5), and the two polar nuclei fusing (C) to form the primary endosperm 

 nucleus. CALIWELL. 



polar nuclei, is known as the primary endosperm nucleus 

 or the definitive nucleus. 



