394 



MORPHOLOGY OF GYMNOSPERMS 



before the walls disappear the jacket cells become binucleate, the 

 nuclei dividing mitotically and amitotically. Mitotic divisions may 

 occur simultaneously in every cell of both layers of the jacket, or every 

 division may be amitotic, or both kinds of division may occur in the 

 same jacket. Amitotic divisions occurring at the upper end of the 

 archegonium might pass easily for fusions. In some jacket cells the 



Fig. 445. — Ephedra: A, young ovule; B, upper part of female gametophyte 

 after fertilization, showing the free cells of the proembryo within the two eggs; X64; 

 C, suspensors developing from the free cells, passing from the egg into the endosperm, 

 and each bearing at the tip an embryonal cell; X64; D-F, later stages in the develop- 

 ment of the embryo; XiS4; A, E. campyJopoda; B-F, E. altissinia. — After Stras- 

 BXJUGER (3). 



nucleus enlarges and becomes surrounded by delicate cytoplasmic 

 radiations such as appear in connection with the unfertilized egg, 

 suggesting the possibility of apogamy, but an investigation of thou- 

 sands of ovules failed to discover any evidence that these egglike 

 jacket nuclei ever function in the production of embryos. It is evi- 

 dent that Miss Berridge and Miss Sand ay (22) discovered the same 

 situation in Ephedra distachya, although they interpreted it differ- 



