422 BOTANICAL GAZETTE [FEBRUARY 
zygous with respect to this character, would demand equality in the 
average numbers of the two sexes; but each year Lychnis dioica has 
produced on the average a considerable excess of females, while the 
ratios in different families range all the way from less than 5 per cent. 
female to nearly go per cent. female. The percentages of females 
in 135 families reared during the summer of 1909 are shown in the 
form of a variation curve in fig. r. It is difficult to believe that a 
family of 4 females and 100 males or of 87 females and 10 males is 
theoretically referable to a ratio of 1:1. In ‘1909 my cultures of 
Lychnis dioica, taken collectively, consisted of 6366 females and 
4831 males (including hermaphrodites), or a ratio of 1.32:1, which 
agrees very well with ratios between 1.20:1 and 1.40:1 reported by 
STRASBURGER (II). After carrying on extensive experiments on 
the influence of various environmental factors, with negative results, 
STRASBURGER reached the conclusion that the sex ratio is determined 
by inherent factors. This is only another way of saying that it 1s 
hereditary in some sense. I have been attempting for several years 
to test the heredity of the sex ratios, but have not yet found the key 
to the situation. It is hoped that the numerous crosses which have 
been made will in the near future throw some light upon the signifi- 
cance of these exceedingly variable ratios and allow the causes which 
determine them to be understood. 
In order to compare the variation in these sex ratios with that in 
a character known to be Mendelian, I have plotted curves representing 
the percentage of females and the percentage of purple- -flowered 
individuals in all families (94 in number) raised during the years 
1907, 1908, and 1909, which were produced by the union of hetero- 
zygous purple with white (see fig. 2). The variation constants of the 
two curves appear in the following table: 
TABLE IV 
VARIATION CONSTANTS OF CURVES CONTRASTED IN fig. 2 
Percentage femal Percentage purples 
ieee cas ee 64.223 +0.630 52.606 +0.55! 
Senked deviation. ee 9.051 40.445 7.925 0-490 
Coe akties he variability. eee eae 14.784 +0.742 15.064 gee 
Theoretical mode. esc eecsck Gag 26.686 52.353 +0-6 6 
Cocticient prs skewness............. — 0.09904 0.0062 +0.02824+ 0.0002 
