494 
Journal of Agricultural Research 
Vol. XXVII, No. 7 
Six individuals were selfed in each of the F 2 progenies and from these 
24 F s progenies were grown in 1923. 
In addition to the hybrid populations, progenies descended from each 
of A the four parents of the crosses were grown each year. Endeavor was 
made to have the several parental and hybrid populations situated so 
as to eliminate environmental effect but soil heterogeneity at the Sacaton 
Station is so pronounced that the endeavor was not wholly successful. 
It is believed, however, that this factor did not impair the validity of 
the comparisons. 
For convenience, the term “spotless” will be used henceforth to 
designate populations in which the spot is absent or very weakly devel¬ 
oped. The latter condition is much the more frequent, for very few 
plants were found on which all of the flowers lacked even a faint trace 
of the spot. Populations in which the development of the spot ap¬ 
proached the Pima norm will be designated “spotted.” Strictly speak¬ 
ing, the allelomorphs here involved are expressed as spotless to faintly 
spotted, on the one hand, and full spotted on the other. 
THE FIRST GENERATION OF THE CROSSES 
Table II gives the frequency distributions and statistical constants 
for the parental and T? 1 progenies grown in 1921. For the reason given 
in another publication 5 , it is considered preferable to use the standard 
deviation rather than the coefficient of variation as an expression of the 
variability of a character determined by grading. 
The data show almost complete dominance of petal spot in the first 
generation, although the mode of each F x progeny is a full grade lower 
than that of the corresponding spotted parental population and the F t 
mean is in each case significantly lower than the parental mean. The 
variability of Fj, as indicated by the standard deviation, is of the same 
order of magnitude as that of the parental populations. 
Table II .—Frequency distributions and statistical constants, for petal spot grade , of the 
parental and F l progenies grown in 1921 
» Kearney, Thomas H. segregation and correlation op characters in an upland-egyptian 
COTTON HYBRID U. S. Dept. Agr. Bui. 1164, p. 13. I 9 » 3 . 
