LENGTH OF COTTON FIBER FROM BOLLS AT 
DIFFERENT HEIGHTS ON THE PLANT 1 
By Thomas H. Kearney, Physiologist in Charge, and George J. Harrison, 
Field Assistant, Alkali and Drought Resistant Plant Investigations, Bureau of 
Plant Industry, United States Department of Agriculture 
The belief is current that in long-staple cottons fiber from the first picking is 
shorter than that from later pickings. This belief is probably well founded, for 
in 33 individual plant selections of the Yuma variety of Egyptian cotton, fiber 
from the second picking averaged one-sixteenth inch (1.6 mm.) longer than fiber 
from the first picking. 2 
The bulk of the fiber obtained from the first picking is taken from bolls on the 
lower fruiting branches, while the later pickings are furnished, in large part, by 
bolls situated higher on the plants. It is of interest, therefore, to determine the 
length of the fiber from bolls borne at different heights on the plant, in order to 
ascertain whether fiber length is correlated with the position of the boll. This 
paper gives the results of such determininations on the Pima variety of Egyptian 
cotton, grown under irrigation at the United States Field Station at Sacaton, 
Ariz. 
Ten well-grown plants of Pima cotton were selected and a ripe boll was gathered 
from each successive fruiting branch on each individual. In order to determine 
whether these plants differed significantly in mean length of fiber, the fiber was 
measured on one seed from each boll collected on each individual. 3 The plant 
means as thus determined are given in Table I. 
Table I. —Mean fiber length of the 10 plants of Pima cotton used in determining 
the relation between height of fruiting branch and length of fiber 
Plant No. 
Number 
of deter¬ 
mina¬ 
tions 
| 
Mean length j 
of fiber j 
Plant No. 
Number 
of deter¬ 
mina¬ 
tions 
Mean length 
of fiber 
1 
Millimeters \ 
Millimeters 
1 
12 
40. 7±0. 57 
6__ 
12 
41.0±0.31 
2 
13 
41.9± .66 
7.. 
12 
43.1± . 94 
3 _. 
13 
41.0± .31 
8_ 
11 
41.9± .40 
4 _ 
13 
42. 5=b . 75 
9..— 
12 
40. 7± . 67 
5 
11 
41. 6± .41 
10___ 
11 
41.9± .30 
The individual plants show a range in mean fiber length amounting to 2.4 mm. 
but the difference between the plants having the longest and shortest fiber, 
respectively, is not significant, being only slightly more than twice its probable 
error. In computing the mean length of fiber for successive heights on the 
plant, it was therefore considered proper to take the bolls from all 10 plants as 
one array. 
1 Received for publication April 9, 1924. 
* Kearney, T. H. fiber from different pickings of Egyptian cotton. U. S.*Dept. Agr., Bur 
Plant Indus. Circ. 110: 37-39. 1913. 
* For a description of the method used in determining length of fiber see: Kearney, T. H. segregation 
AND CORRELATION OF CHARACTERS IN AN UPLAND-EGYPTIAN COTTON HYBRID. U. S. Dept. Agr. Bui. 1164, 
p. 10. 1923. 
Journal of Agricultural Research, 
Washington, D. C. 
( 563 ) 
Vol. XXVIII, No. 6 
May 10, 1924 
Key No. G-411 
