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. 



eggs 



Pig. 390. 



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

 gs at lelt, 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. 



656. Fertilization. When the 

 pollen tube has reached the em- 

 bryo sac (paragraph 652) it opens 



Macrospore (one-celled stage) of lilium. an d the 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 



Fig. 391. 



