232 
Journal of Agricultural Research 
VoL XXI, No. 4 
Table II .—Frequency distributions for the characters fiber length, lint index, and seed 
fuzziness of a progeny of the parent plant of the Pima variety, of a “bulk” {contin¬ 
uously open-pollinated) population of strain 3-3, and of a line of the same strain which 
was strictly self fertilized during five generations , each population containing 32 plants 
FIBER LENGTH 
Quauty of fiber. —While no quantitative data on this point are 
available, it seemed evident in examining the samples of fiber from the 
individual plants of the three stocks that those of the “parent” progeny 
differed more among themselves in smoothness, luster, and color than 
did the plants of the “bulk” stock and of the selfed line. The smooth¬ 
ness or silkiness of the fiber also seemed to average higher in the two 
latter populations. Selection, therefore, would seem to have resulted in 
raising the mean of this character and in reducing its variability. 
Lint index. —The abundance of the fiber, as expressed by the mean 
weight of fiber borne by 100 seeds, averaged 36 % per cent greater in 
the “bulk,” or commercial stock of the variety, than in the progeny of 
the original Pima plant. The difference between the means is very 
significant, amounting to 19 times its probable error. There had been 
also a significant reduction in variability, the coefficient of variation 
for lint index of the “bulk” stock being lower than that of the “parent” 
progeny by an amount equivalent to more than 4 times the probable 
error of the difference. Since increase in the abundance of fiber on the 
seed, like increase in length of fiber, has been one of the principal objec¬ 
tives of the breeding work with the Pima variety, it is interesting to 
