POLY EM BRYONY 



347 



an intermediate type, some ovules of an ovary follow the course 

 outlined for the first race and others for the apomictic race. 



Embryos Originating from Other Embryo Sacs in the Ovule. As 

 mentioned in the introductory paragraph, the polyembryonate 



Fig. 196. Origin of embryos from antipodal cells. A,B, Ulmus glabra; embryo 

 sacs with egg-like antipodal cells. C, U. glabra, embryo sac, showing z}'gotic 

 embryo at micropylar end and antipodal embryo at chalazal end. (After Ekdahl, 

 1941.) D, Allium odorum; embryo sac, showing two embryos, one derived from 

 egg and the other from antipodal cell. (After Modilewski, 1931.) E, Elatostema 

 sinuatum eusinuatum; embryo sac with three antipodal embryos, of which one is 

 several-celled, another two-celled, and the third undergoing first division; note egg 

 embryo at upper end. (After Fagerlind, 1944-) 



condition is sometimes due to the occurrence of multiple embryo 

 sacs within the ovule. These may arise (1) either from the deriva- 

 tives of the same megaspore mother cell, or (2) from two or more 

 megaspore mother cells, or (3) from nucellar cells (apospory). 



