1922] STOUT—STERILITY III 
parts in seed formation, may be obtained by experimental means 
from a study of the fluctuations in fertility that are to be seen in 
those feebly self-compatible individuals which are to be found in 
species in which general sexual incompatibilities are strongly 
developed. 
A subsequent report of a more detailed study on this problem 
(Stout 11), however, showed that in Verbascum phoeniceum, 
Eschscholizia californica, and Cichorium Intybus the various grades 
of self-compatibility operate very uniformly throughout the entire 
period of bloom, and that there are in the feebly self-compatible 
plants of these species no specially marked tendencies to self- 
compatibility at any definite phase of the blooming period. It was 
also found that in Nicotiana Forgetiana Hyb. Hort. and in Lythrum 
Salicaria end-bloom self-compatibility develops as an infrequent .- 
individual variation rather than as a phenomenon characteristic of 
the self-compatible plants. In these species there is no cyclic pro- 
duction of fruits and seeds which would indicate a general relation 
between vegetative vigor and the development of self-compatibility. 
Such a cyclic occurrence of self-compatibility was found, 
however, and reported for Brassica pekinensis, and it was noted 
that the highest degree of self-compatibility attained by any given 
plant appeared very uniformly during the period of mid-bloom. 
Further studies with this species have since been made which show 
this to be the rule for all those individuals that are self-compatible 
in any degree. Similar behavior has also been found in cultures of 
Brassica chinensis and in hybrids between this species and B. 
pekinensis. So far as known to the writer, this is the most uniform 
and definite case of a general and definite periodicity in the modifi- 
cation of sexual compatibilities within a blooming period. In 
these species, also, flower abortion appears in the transition of 
vegetative to reproductive vigor, exhibiting an influence of vege- 
tative vigor on the morphological development of flowers. 
Material and methods 
Several strains of the “head” sorts of Brassica pekinensis, 
commonly known as Chinese cabbage or Pe-tsai, and one strain of 
the loose-leaved or headless sort (the Nanking variety) were grown 
