A densely pubescent mutant, 61038, with hairy anthers was isolated as a pilose upland cotton which conferred resistance to spider mites and showed more trichomes on the plant body than the T₁ pilose phenotype. Genetic studies indicated that the mutant is conditioned by one dominant gene that is allelic to the pilose gene T₁, hence it is designated T₁^a. The trichomes are of two types: stellate and simple. This mutant had many more stellate trichome branches (10-50 times) than normal pubescent cottons, while its simple trichome density was only 2-5 times higher. Another hairy anther mutant was isolated from interspecific crosses between upland cotton with T₁ and Pima cotton. No hairy anther plants were observed in more than 1500 F₂ plants from 17 interspecific crosses between long-staple and upland cotton without T₁. We propose a model where a dominant inhibitor gene, I_t, from upland cotton inhibits T₁ expression on anthers. Double recessive status at both loci in the Pima cottons, when combined with T₁ from upland cotton, results in expression of the hairy anther phenotype (T₁_ I_t I_t) in the F₂.