PLANT BREEDING 355 



for constant intermediate hybrid races which I think has never before 

 been mentioned. In crossing species of the genus Nicotiana, I have 

 had plants develop from seed that have apparently been formed 

 apogamously, that is, formed from an immature egg cell without fer- 

 tilization. It is evident that this is induced by the extraordinary irri- 

 tation of foreign pollen. The true hybrid plants that are formed are 

 generally blends in the first generation. The question, then, arises : 

 May not the. difficulty of maturing sexual cells in a wide cross some- 

 times cause apogamous development and therefore a continued propa- 

 gation of a constant and uniform race? 



All but the last of these suggestions may also be pertinent in the 

 case of varietal crosses where there is said to be a blending of char- 

 acters that deal with size. I am not certain, however, that all the so- 

 called blend hybrids might not show segregation if studied in large 

 numbers. I have found such segregation in size characters in crosses of 

 both maize varieties and of tobacco varieties. 3 



3 In the writer's paper " The Role of Selection in Plant Breeding " in the 

 August number of this journal, the legends for figures three and four unfor- 

 tunately were interchanged in printing. 



