Two Upland (Gossypium hirsutum) varieties (Kapas Purao and Philippines Ferguson) and apunctatum cotton of unknown origin, were all shown to carry a key hairiness gene at theH₁ locus. This gene is so closely linked withchl₁ (one of the two complementary genes governing chlorophyll deficiency) that transferences of it to Sakel, which carrieschl₂, cannot produce strains homozygous for hairiness. This allele has been calledH₁^k, and it is considered probable that theH₁^k-chl₁ segment of chromosome is invertedvis-à-vis theH₁-Chl₁ segment in Sakel and in_{G. barbadense} in general, andvis-à-vis theH₁-chl₁ segment in MU8b and other_{G. hirsutum} varieties.

In addition toH₁^k, Ferguson carries modifying genes which lengthen the hairs, minor H genes which can themselves directly confer hairiness, and modifying genes reducing the density of hair population.