Studies in Plant Hybrids: The Spermatogenesis of Hybrid Peas* 



By William Austin Cannon 

 (With Plati-.s 17-19) 



Up to the present the studies on the origin and development 

 of the spores and sex-cells of hybrids have been made with no 

 definite knowledge of the manner of the variation of the hybrid 

 race and without regard to or accurate knowledge of the degree 

 of fertility or sterility of the forms, and it seems almost unneces- 

 sary to remark that no study can be at all complete, whatever its 

 results or conclusions may be, that does not take into considera- 

 tion each of these conditions. 



Studies on the sporogenesis and spermatogenesis of hybrids in- 

 clude the researches on cannas by Guyer.f on cotton by Cannon, 

 on Drosera by Rosenberg, on Gladiolus by Metcalf, on pigeons by 

 Guyer and on Syringa by Juel. Nothing definite is known, so far 

 as I am aware, about the variation of any of these hybrids, and 

 as regards their fertility probably not one is entirely fertile, and 

 Syringa at least is thought to be quite sterile. 



There are two or three conditions at least to which a hybrid 

 plant should conform in order to be well adapted for study from a 

 morphological standpoint. These are briefly : the hybrid must be 

 fertile ; it must vary in a definite and known manner ; and, finally, 

 it must be suitable in itself, as distinguished from all other require- 

 ments, for histological study. 



One reason why the pea hybrids are so well adapted to experi- 

 mental researches is that they are fertile. This, indeed, was one 

 of the reasons that led Mendel to select them for his studies. I 



*This study was made with the aid of Grant No. 27 of the Carnegie Institution, 

 t See bibliography at the end of this paper. 



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