Gossypium L.

11. Gossypium L. View in CoL 2

Shrubs or woody annuals, irregularly dotted with black oilglands. Flowers solitary in the leaf-axils. Epicalyx-segments 3, free, broadly ovate to deltate, cordate. Calyx cupuliform, with 5 short teeth or lobes. Styles united; stigmas terminal, capitate, more or less united. Fruit a 3- to 5-locular, loculicidal capsule; seeds numerous, hairy. The cultivated cottons (which include all the European plants) differ from the wild species in having flattened, twisted (‘lint’) hairs on the seeds. This character seems to have developed under the influence of human selection. The same influence is responsible for the stabilization of the annual habit, which is found only in cultivated plants, and which has enabled the cultivation of cotton to be carried on in regions with a cold winter climate. No chromosome counts have been made on European plants, but G. herbaceum , like all Old World species, is known to be diploid, with 2n = 26, while G. hirsutum is one of the New World tetraploids, with 2« = 52. Diploids also occur in the New World.

Literature: J. B. Hutchinson, R. A. Silow & S. G. Stephens, The Evolution of Gossypium . London, etc. 1947. G. Watt, The Wild and Cultivated Cotton Plants o f the World. London. 1907.

Teeth of epicalyx-segments usually less than 3 times as long as wide; filaments 1-2 mm, ± equal 1. herbaceum Teeth of epicalyx-segments usually more than 3 times as long as wide; filaments 4-6 mm, the upper longer than the lower

2. hirsutum