24 
BULLETIN 1365, U. S. DEPARTMENT OF AGRICULTURE 
factor has but slight direct effect on boll periods, as the inner bolls 
shown in Table 16, other than the exception just mentioned, matured 
more rapidly than those of the same date farther out on the fruiting 
branches, although the latter were exposed to much more light. 
The average boll period for each node of the fruiting branches on 
the main stalks of the Pima and Acala plants in the 1924 and 1925 
seasons and the average period of all the bolls produced by the main 
stalks in these seasons are given in Table 17. In comparing the boll 
periods of the specific nodes of the Pima branches with those on the 
same nodes of Acala branches in 1924, the Acala is seen to have 
developed mature bolls in 5 to 7 days less time than the Pima. In 
1925 the Acala bolls on nodes 4 to last required as long to mature 
as those in the same position on the Pima, but the other nodes of 
Acala branches developed mature bolls in considerably less time than 
corresponding nodes of Pima branches. The difference each season 
between the periods of all bolls of the two varieties showed that bolls 
of Acala ripened in about 5 days less time than those of Pima. Nearly 
as great a difference in the average square period existed between the 
two varieties, and the average time from the appearance of a square 
until it reached maturity as an open boll was 9 or 10 days less for 
the Acala than for the Pima. 
Table 17. — Average boll period for each node on fruiting branches borne by the 
main stalks of 20 plants each of Pima and Acala cotton in 1924 o:nd 1925 and 
the average period of all bolls produced by the main stalks in these seasons 
Pima 
Acala 
Season and fruiting branch node 
Number 
of bolls 
Average 
maturing 
period (days) 
Number 
of bolls 
Average 
maturmg 
period (days) 
Season of 1924: 
1 
144 
33 
13 
267 
256 
161 
79 
38 
534 
56. 681±0. 261 
58. 455± . 441 
62. 061± . 734 
65. 077±1. 235 
58. 266± . 239 
61. 020± . 308 
62. 969± . 351 
64. 430± . 376 
65. 184± . 329 
62. 408± . 196 
63 
40 
31 
14 
148 
112 
71 
23 
14 
220 
51. 810±0. 531 
2 
52. 175± . 581 
3 
54. 839± . 705 
4 to last . 
58. 000±1. 078 
1 to last .. . . 
53. 12S± . 338 
Season of 1925: 
i. 
55. 339± . 483 
2 
55. 887± . 586 
3 
61. 130±1. 337 
4 to last 
65. 071±1. 68S 
1 to last .. 
56. 741 ± . 378 
BOLL PERIODS AFFECTED BY FRUIT ON PRECEDING NODES 
An attempt was made to find whether the presence of bolls on the 
inner nodes of the fruiting branches caused a lengthening of the 
period required for bolls to reach maturity on the outer nodes. This 
was determined by comparing the maturing periods of bolls of the 
same date on a specific outer node of the fruiting branches when the 
preceding node bore a boll and when the preceding node was vacant. 
Only one case was found in which there were enough bolls in each of 
the necessary combinations for accurate information to be obtained. 
This case was found in the Pima variety in 1924 when the periods for 
bolls on node 2 produced from flowers of August 8 to 17 were com- 
pared in two groups — when a boll was present on node 1 and when 
node 1 was vacant. The mean period for bolls at the second node 
when the inner node was vacant was 61.778 ±0.782 days, but when 
