CHARACTERS IX AX UPLAND-EGYPTIAN COTTON HYBRID. 
35 
[Table 9. — Coefficients of correlation between the F z progeny means and the values of the 
corresponding F 2 parents of the Holdon-Pima cotton hybrids. 
Character. 
Coefficient 
of 
correlation. 
Axis: 
Length 0.79±0.054 
Internode number 55± -100 
Internode length 74— . 065 
Fruiting branch: 
Length 57± . 099 
First internode 61± . 090 
Leaf: 
Length 46± .113 
Width 35± .126 
Index 63- . 0S7 
Lobe index 87 ± .035 
Character. 
. Coefficient 
of 
correlation. 
Leaf: 
Vein angle 0. M±0. 042 
Callus color ~:~ . 058 
Petiole hairiness 78± .056 
Petal: 
Color 65± .083 
Spot S6± .037 
BoU: 
Length 75± .064 
Diameter 50± .108 
Index 63= . 0^7 
Lock number 81± . 049 
COMPARATIVE VARIABILITY OF THE F 3 PROGENIES AND OF THE Fj AND PARENTAL 
POPULATIONS. 
Table 10 gives, for each character determined in F 3 in respect to 
which definite Mendelian segregation was not shown in F 2 , the coeffi- 
cient of variation (of measured characters) or standard deviation (of 
graded characters) of the most variable and of the least variable F s 
progeny grown in 1920 and the corresponding constants for the par- 
ental and F 2 populations grown in 1919. In the last three columns 
of the table are shown the significance of the differences, as expressed 
by the value obtained by dividing the difference by its probable error, 
between the most variable and least variable F 3 progenies, between 
the most variable F 3 progeny and the F 2 population, and between 
the least variable F 3 progeny and the parental population which was 
the less variable as regards the character in question. 
The data given in Table 10 permit the following conclusions, the 
expressions "most variable" and "least variable ,? referring always to 
the individual character and not to the general variability of the 
population : 
The coefficients of variation or standard deviations of the most variable and of the 
least variable of^ the F 3 progenies differed significantly for all characters, the value 
obtained by dividing the difference by its probable error ranging from 3.4 to 9.6. 
The coefficient of variation or standard deviation of the most variable of the F 3 
progenies was higher than that of the F 2 population in respect to all characters, 
although for only 3 characters were the differences apparently significant. 
The coefficient of variation or standard deviation of the least variable of the F 3 
progenies differed significantly from that of the less variable parent in respect to only 
3 of the 18 characters, the least variable F 3 progeny showing significantly less 
variability for 1 character and significantly greater variability for 2 characters. In 
respect to the 2 latter characters, the least variable F 3 progeny was not significantly 
more variable than the more variable parent. 
The assumption seems justifiable that if segregation has taken place 
in F 2 the progenies of second-generation individuals at either extreme 
of the F 2 distribution should be less variable than progenies of 
individuals representing the F 2 mean. As expressed bv Freeman (19, 
p. 20): 
If the differences in the means of the F 3 cultures * * * are duo to genetic 
causes, one would expect the intermediate cultures to be more variable than the 
extremes, thus assuming that the extreme cultures are more nearly homozygous than 
those which are intermediate. 
This test was applied to the 22 F 3 progenies of the Holdon x Pima 
hybrid. The results are stated in Table 11, which shows, for each of 
