1911. | Experimental Studies in Indian Cottons. 449 
and red sap colour, which are absent in Type 9) is found to hold within a 
fair degree of approximation. The correctness of the supposition here made 
is shown by the behaviour of a cross between Type 3 and Type 4. In this 
ease the yellow character is present in both types, and a simple pair of 
allelomorphic characters is under consideration. 
3. Leaf Factor—The degree of incision of the leaf lobe has formed the 
basis of most classifications of the Indian cottons. This character has been 
found capable of a numerical expression, to which the term leaf factor has 
been applied by the author.* This character of the leaf—a multiple organ— 
is, within limits, a plant character also, and may be fully defined as the 
average factor of all leaves arising from the monopodial branches of the 
plant. 
Pure types have been found to fall into two groups—a broad-lobed, with 
a leaf factor < 2, and a narrow-lobed, with a leaf factor >3. In no case 
has purity of this character been found in the offspring of a plant with 
a leaf factor intermediate between these two values. 
When crossing occurs between a broad- and a narrow-lobed type, the 
heterozygote has a leaf factor which is approximately the arithmetic mean 
of those of the two parental types. In the F, generation a series of forms is 
obtained, in which every value of leaf factor is found. The distribution of 
individuals is, however, not uniform, but shows a definite arrangement into 
three groups, whose mean values agree approximately with those of the two 
parental types and the Fy, heterozygote. The curve obtained by plotting 
“such a series is trimodal, the three modes corresponding respectively to the 
two parental and the intermediate values. In subsequent generations the 
average leaf factor of the offspring approximates to that of the parent. In 
othér’ words, narrow- and broad-lobed plants will be found to breed pure, 
while the intermediate forms, though they may give a series of individuals 
with varying values of leaf factor, will give a larger proportion of broad- or 
narrow-lobed offspring, according as they themselves possess a leaf factor 
approximating to the broad- or to the narrow-lobed types. 
4. Type of Branching and Length of Vegetative Period—As has been noted, 
the secondary branches of the cotton plant may be either monopodial or 
sympodial, and in some types the secondary branches are, with the exception 
of a few of the basal ones, all sympodial, while in others, with the exception 
of only a few apical branches, they are all monopodial. In the latter case ~ 
the vegetative period is prolonged, and no fruit is formed until the tertiary 
branches are developed. The type of branching, therefore, can be recorded 
in two ways, either by the fraction of the main stem, measured from the 
* © Journ. As. Soc. Bengal,’ vol. 4, p. 13. 
