GAMETOPHYTE AND SPOROPHYTE. 



231 



synergids. The egg cell is all that remains of the archegonium 

 in this reduced prothallium. The three nuclei at the lower end 

 are the antipodal cells. 



Fig. 302. 



ynergids and egg at 



Podophyllum peltatum, ovule containing mature embryo sac ; two s 

 left, endosperm nucleus in center, three antipodal cells at right. 



455. Embryo sac is the young female prothallium. In 



figures 303, 305 are shown the different stages in the develop- 

 ment of the embryo sac in lilium. 

 The embryo sac at this stage is 

 the young female prothallium, and 

 the egg is the only remnant of the 

 female sexual organ, the arche- 

 gonium, in this reduced gameto- 

 phyte. 



456. Fertilization. Before 

 fertilization can take place the / 

 pollen must be conveyed from 

 the anther to the stigma. (For 



the different methods of pollination see Part III.) When the 

 pollen tube has reached the embryo sac, it opens and the sperm 

 cell is emptied into the embryo sac near the egg. The sperm 

 nucleus now enters the protoplasm surrounding the egg nucleus. 

 The male nucleus is usually smaller than the female nucleus, and 

 sometimes, as in the cotton plant, it grows to near or quite the 



Fig. 303- 

 Macrospore (one-celled stage) of lilium. 



