1922] STOUT—STERILITY 131 
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 Mosrus, Vécutinc, Kress, SAcus, and GoEBEL, and recent 
papers by GARNER and ALLARD 5 and 6, and by SETCHELL 9g). 
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 = life of the 
individual. 
New Yorxk Boranicat 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. 
- Correns, C., Die geschlechtliche Tendenz der ee gemischt- 
geschlechtiger Pflanzen. Zeitschr. Bot. 12:49-60. 1 
3- COULTER, JoHN M., Evolution of sex in plants. Chae. 1914. 
N 
