It has been possible to recognize particular members of the gene complex controlling number of lint hairs on the cotton seed by their effect on the glabrous lintless mutation. The latter was used as an analyser to separate the genes controlling lint development into two series, those hypostatic to it, and those epistatic to it and acting as modifiers. The basic lint percentage effect of a single epistatic gene in the heterozygous phase is about 6–10% on the lintless genotype. The epistatic genes show a reductive interaction with other genes working towards the same effect, so that in the fully linted genotype their effect is less than one-fifth of their basic value.

The epistatic genes are shown to have a clearly defined varietal and specific distribution, not associated with the ginning capacity of the strains in which they occur, showing that in different taxonomic groups a typical quantitative character may be controlled by quite distinct complexes of genes.