i 9 22] STOUT— STERILITY 13 1 



is decidedly against such a view. The loss of maturity, as seen 

 especially in the complete failure of flower formation, has very 

 universally been shown to be due to the indirect influence of such 

 external factors as light, heat, and nutrition on the metabolism 

 and attending correlations in the organism (see numerous papers 

 by Mobius, Vochting, Klebs, Sachs, and Goebel, and recent 

 papers by Garner and Allard 5 and 6, and by Setchell 9). 



That species or strains showing flower abortion and physiological 

 incompatibility are different genetically from others that do not 

 show such sterilities is obvious. That these types of sterility are 

 more completely hereditary in some species than in others is clear. 

 That these characteristics are not definitely and directly represented 

 as such in the germ plasm by hereditary units is very evident 

 from the results of genetical studies. Self-compatibility and self- 

 incompatibility especially are not found to be alternative conditions 

 in tests by crossing or in line breeding; the heredity is decid- 

 edly irregular and sporadic even when compatibilities are not 

 cyclic in their appearance as they are in Brassica chinensis and 

 B. pekinensis. 



The various types of sterility seen in these species of Brassica 

 decidedly indicate a mutually limiting relationship between vege- 

 tative and reproductive vigor. Their irregular inheritance, their 

 appearance at definite periods in the cycle of development of the 

 plant as a whole, and especially the cyclic manifestation of self- 

 compatibility, indicate that the morphological and physiological 

 differentiations of sex are regulated and determined by those 

 internal and biogenetic processes which in general determine the 

 cycle of growth, development, and maturity in the life of the 

 individual. 



New York Botanical Garden 

 Bronx Park, N.Y. 



LITERATURE CITED 



1. Child, C. M., Certain aspects of the problem of physiological correlation. 

 Amer. Jour. Bot. 8:286-295. 1921. 



2. Correns, C, Die geschlechtliche Tendenz der Keimzellen gemischt- 

 geschlechtiger Prlanzen. Zeitschr. Bot. 12:40-60. 1920. 



3. Coulter, John M., Evolution of sex in plants. Chicago. 1914. 



