May 16, 1931 
Heritable Variations in Cotton 
237 
Two plants, selected in progeny 5-3-10 of 1914 and designated 5-3-10-4 
and 5-3-10-6, gave rise to strains of which progenies were grown in 
1916, 1917, and 1918. Measurements of the weight of seed cotton per 
boll, length of fiber, lint index (weight of fiber per 100 seeds), and fuzzi¬ 
ness of the seeds were made in each year upon plants of each strain. 
Consistent and significant differences were found only in regard to the 
character seed fuzziness. The means of the grade numbers of the indi¬ 
vidual plants are given in Table VI. 
Tabus VI. —Means for seed fuzziness of two closely related lines of the Pima variety , 
grown in 1916 1 1917, and. 1918 
Group or strain. 
\ 
1916 
1917 
1918 
Number of 
plants. 
Mean 
grade. 
Number of 
plants. 
Mean 
grade. 
Number of 
plants. 
Mean 
grade. 
5-3-IO-4. 
16 
3 - 9 ±o. II 
47 
3.2±o. 17 
71 
3 - 3 ± 0.10 
5-3-10-6. 
29 
4 - 4 ± - 11 
35 
.15 
28 
4 - 3 ± .10 
Difference. 
• 5 ± -155 
.6± .226 
i.o± .142 
Strain 5-3-10-6 is consistent in having had fuzzier seeds in each of the 
three years, although the difference in 1917 was scarcely significant. 
This case affords clear evidence of a slight but heritable difference be¬ 
tween two lines which are very closely related, and of which the common 
ancestor (plant 5-3-10 of 1913) represented the third generation of line- 
bred descent from the parent plant of the Pima variety. 
INHERITANCE OF AN INCREASED NUMBER OF BOLL LOCKS 
The boll of Pima cotton has usually 3 locks or carpels, although 4-lock 
bolls are borne by nearly all plants of this variety and bolls having 2 or 5 
locks are met with occasionally. There is much individual variation in 
the proportion of 3-lock and 4-lock bolls. With a view to ascertaining 
whether such differences are heritable, several plants which had more or 
fewer 4-lock bolls than the average were selected in 1917 in an increase 
plot of a selected strain of Pima. Progenies of three such plants were 
grown in 1918 from seed produced by open-pollinated flowers. Table 
VII gives the percentages of bolls with 4 locks, all bolls on all plants in 
each progeny having been taken as one array in computing the percentage 
and its probable error. 
Table VII .—Percentages of 4-lock bolls in the progenies of individual plants selected in 
1917 
Progeny. 
Number 
of plants. 
Percentage of 
4-lock bolls. 
No. 2 (from parent with few 4-lock bolls).,. 
' 19 
22 
8 
4- 6±. 031 
5 - 9±-33 
IO. 5±. 67 
No. 1 (from parent with many 4-lock bolls). 
No. 3 (from parent with many 4-lock bolls). 
36732°—21 - i 
