Feb. 16,1924 
Inheritance of Petal Spot in Pima Cotton 
509 
bolls in both crosses is somewhat below the average of the parental 
means, but is significantly higher than the percentage of the normal or 
spotted parent. The heritability of this character is shown further by 
the fact that in F 2 the cross involving 3-2-4, the spotless family having 
the higher percentage of 4-lock bolls, gave a mean percentage of 4-lock 
bolls nearly twice as great as the cross involving spotless family 1-3-12. 
Expressed as a percentage of the lower mean, the difference between the 
hybrids (F 2 ) amounted to 89 per cent while the difference between the 
spotless parental progenies grown the same year (1922) amounted to 
131 per cent. 
Table XV .—Percentages of 4-lock bolls in the parental and hybrid populations grown in 
1921 and 1922 
Populations of 1921. 
Num¬ 
ber of 
plants. 
Mean percent¬ 
age, 4-lock bolls. 
Populations of 1922. 
! 
i Num¬ 
ber of 
1 plants. 
| 
Mean percent¬ 
age, 4-lock bolls. 
PARENTAL 
PARENTAL 
! ; 
| ■. 
1 
1-3-12-14 (spotless)... 
14 
4 - I 5±o. 34 
1-3-12-14-2 (spotless) 
22 
4 - S 4 ±°- 37 
12 (spotted). 
20 
2. 45± • 21 
12-13 (spotted). 
*9 
1. 84 ± . 15 
Difference. 
1. yo± . 40 
Difference. 
2. 70± . 40 
HYBRID (Fi) 
HYBRID (F 2 ) 1 
I-3-I2-I4X12. 
28 
4. 5o± . 28 
1-3-12-14 Xi2«.| 
83 
2. 7I± . 13 
PARENTAL 
l 
parental 
3-2-4-1 (spotless). 
27 
9 - 3 I ± -33 
3-2-4-1-22 (spotless). 
26 
10- 5 °± - S 3 
13 (spotted). 
14 
2. 92 ± . 24 
13-8 (spotted).1 
22 
2. 44 ± .24 
Difference.i 
6. 39 i - 4 i 
Difference. 
8. o6ct . 58 
HYBRID (F^ 
HYBRID (F 2 ) 
2— < 2 —A— tVt? 
33 
5 - 87 ± .30 
" 2 — 2 — A —T "X T 2® I 
I 62 
5 - J 3 ± -23 
j *r x A o . 
O * ......... 
t 
a Two progenies as one array. 
There appears to be no general correlation, either negative or posi¬ 
tive, between the degree of development of the petal spot and the mean 
number of boll locks per plant. In Fj and F 2 of a hybrid between 
upland and Egyptian cottons, the coefficients of correlation for this 
pair of characters were, respectively, — 0.043 ±0.137 and 0.011 ±0.050. 
As concerns the material dealt with in this paper, the coefficient of corre¬ 
lation for 125 plants in the progenies of the spotless families grown in 
1920 was 0.069 ±0.060. The correlations were also worked out for the 
spotted (dominant and heterozygous) plants in the F 2 progenies of 192 2, tak¬ 
ing as one array in each case the two progenies of the cross 1-3-12-14X 12 
and the two progenies of the cross 3-2-4-1X 13. The numbers of plants 
were, respectively, 55 and 48 and the coefficients of correlation obtained 
were —0.045 ±0.091 and 0.148±0.095. 12 A further indication of the 
absence of linkage was afforded by comparison of the mean percentages 
of 4-lock bolls of the spotted and the spotless segregates in each F 2 
progeny. There was in no case a significant difference between the two 
13 The correlations worked out in the upland X Egyptian hybrid were between petal spot grade and 
mean number of boll locks per plant, while in the crosses described in this paper the correlations were 
between petal spot grade and percentage of 4-lock bolls. These are merely different expressions of the 
same relation, practically all of the bolls in this variety of cotton having either three or four locks. 
