Gossypium L.

Scientific Description

Common name. Cotton. Family Malvaceae.

Tribe Gossypieae.

Habit and leaf form. Shrubs, or herbs, or trees (rarely and not in Australia); often evergreen, or deciduous. Plants unarmed. Annual; to 1–3 m high. Mesophytic. Heterophyllous, or not heterophyllous. Leaves medium-sized to large; alternate; spiral; petiolate; non-sheathing; simple. Leaf blades dorsiventral; dissected (3–5-lobed), or entire; ovate, or obovate, or elliptic, or orbicular (or reniform); palmately lobed; palmately veined; cordate. Mature leaf blades adaxially glabrous, or pubescent; abaxially glabrous, or pubescent. Leaves with stipules. Stipules caducous, or persistent. Leaf blade margins entire. Leaf anatomy. Hairs present; complex hairs present. Complex hairs stellate. Extra-floral nectaries present (1, 3 or 5 basal nectary glands on the midrib of the lower surface of the leaves).

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous.

Inflorescence and flower features. Flowers usually solitary, or aggregated in ‘inflorescences’; axillary. Inflorescences axillary; inflorescence of solitary or clustered axillary flowers. Flowers pedicellate (pedicels often articulate); medium-sized to large; regular; 5 merous; tetracyclic. Hypogynous disk absent. Nectariferous glands 3 (present below the insertion of the epicalyx segments). Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present (punctate with black oil glands); 5; 1 -whorled; gamosepalous; lobed, or entire (undulate); lobulate (5-lobed), or toothed (5 toothed); hairy, or glabrous; valvate; exceeded by the corolla; campanulate; regular; persistent. Calyx lobes triangular. Epicalyx present (free persistent bracteoles, shorter than the calyx lobes). Corolla present; 5; 1 -whorled; polypetalous (adnate to the base of the staminal column); regular; often with contrasting markings (usually with a different colour base); white, or yellow, or red, or pink, or purple. Petals obovate. Androecium present. Androecial members indefinite in number. Androecium 50–100 (i.e. ‘many’). Androecial members adnate; all equal; coherent (connate; the filaments fused in a column surrounding the style); 1 - adelphous (the tube attached to the petals); 1 -whorled. Androecium exclusively of fertile stamens (or rather, half-stamens, each having only a half anther). Stamens 50–100. Anthers dehiscing via longitudinal slits; introrse; unilocular. Gynoecium 3–5 carpelled. The pistil 3–5 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary plurilocular; 3–5 locular. Gynoecium stylate. Styles 1; simple; apical. Stigmas 1; 3–5 - lobed; clavate. Placentation axile. Ovules 2–50 per locule (i.e. 2-several).

Fruit and seed features. Fruit 7–50 mm long; non-fleshy; brown to black; not hairy; dehiscent; a capsule (globular to ovoid, rarely fusiform, acute to acuminate, beaked, prominently punctate with black oil glands). Capsules loculicidal (by 3–5 valves). Dispersal unit the seed. Fruit 30–50 seeded (i.e. ‘many’). Seeds not compressed (ovoid); small; arillate, or non-arillate; sometimes conspicuously hairy, or not conspicuously hairy.

Geography, cytology, number of species. World distribution: pantropical. Native of Australia. Not endemic to Australia. Australian states and territories: Western Australia, Northern Territory, Queensland, and New South Wales. Northern Botanical Province. A genus of c. 20–30 species; 16 species in Western Australia; 5 endemic to Western Australia.

Etymology. From the Latin gossypion; name used by Pliny for Gossypium arboreum, cotton tree; derived from Arabic qutn, cotton.