328 



MORPHOLOG Y. 



gids. 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. 390. 



Podophyllum peltatum, ovule containing mature embryo sac; two synergids, and 

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



655. Embryo sac is the young female prothallium. In figs. 

 391-393 are shown the different stages in the development 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. 



*. I ^J 656. Fertilization. When the 

 / pollen tube has reached the em- 

 bryo sac (paragraph 652) it opens 

 Macrospore (one-ceiled stage) of lilium. an( j t he two sperm cells are emptied 

 near the egg. The first sperm nucleus enters the protoplasm 

 surrounding the egg nucleus and uniting with the latter brings 

 about fertilization. The second sperm nucleus often unites 

 with the endosperm nucleus (or with one or both of the "polar 

 nuclei"), bringing about what some call a second fertilization. 

 Where this takes place in addition to the union of the first sperm 



