Parthenogenesis and Vegetative Apogamy 117 



chromosomes. It is evident that for some reason the 

 reduction division had failed in connection with spore 

 formation, so that the spores were diploid, resulting 

 naturally in a diploid gametophyte. In these cases it 

 was found that no reduction division occurred during 

 the life- history, the diploid number continuing through 

 both sporophyte and gametophyte. The interesting 

 observation was made also that parthenogenetic eggs 

 are slower in starting to germinate than those normally 

 fertilized. 



Polyembryony is also common among seed plants, 

 and this involves apogamy. Mention has been made 

 of the case of an onion seed containing five embryos, 

 only one of which could have come from a fertilized egg. 

 The four possible sources of embryos are found to be the 

 fertilized egg, the unfertilized egg, gametophyte cells, 

 and sporophyte cells. 



Another interesting fact concerning parthenogenesis 

 in seed plants has been added comparatively recently (i). 

 A plant known to be parthenogenetic was shown to have 

 2x eggs, but it was also known to be pollinated and its 

 sperms were seen discharged into the embryo sac. These 

 sperms were apparently functional in every particular, 

 and with the x number of chromosomes, and yet, 

 although a sperm came into contact with an egg, there 

 was no fusion. The inference has been that a diploid 

 egg may be incapable of fertilization and is partheno- 

 genetic if it functions at all. It does not follow that only 

 diploid eggs are parthenogenetic, for parthenogenesis 

 in ferns contradicts this conclusion. 



The bearing of these facts upon genetics should be 

 considered. Plant geneticists have been using the most 





