Croton L.

Scientific Description

Family Euphorbiaceae.

Habit and leaf form. Trees, or shrubs, or herbs (rarely); laticiferous, or non-laticiferous and without coloured juice, or with coloured juice. Plants succulent, or non-succulent. Mesophytic, or xerophytic. Leaves small to large; alternate; spiral, or distichous; ‘herbaceous’, or leathery, or fleshy; petiolate (biglandular at junction of petiole and lamina); non-sheathing; gland-dotted, or not gland-dotted; simple (usually). Leaf blades entire; pinnately veined. Leaves with stipules, or without stipules. Stipules minute; caducous, or persistent. Leaves without a persistent basal meristem. Leaf anatomy. Urticating hairs present, or absent. Stem anatomy. Nodes tri-lacunar, or unilacunar. Secondary thickening developing from a conventional cambial ring, or anomalous; from a single cambial ring.

Reproductive type, pollination. Fertile flowers functionally male, or functionally female. Unisexual flowers present. Plants monoecious. Male flowers without pistillodes. Entomophilous.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in racemes (usually androgynous, the female flowers sometimes reduced to 1 basal, long-pedicelled flower). Inflorescences terminal, or axillary. Flowers bracteate, or ebracteate; minute to small; regular. Floral receptacle developing an androphore, or with neither androphore nor gynophore. Free hypanthium absent. Hypogynous disk present. Perianth with distinct calyx and corolla, or sepaline; 5, or 10; 1 -whorled, or 2 -whorled; when two-whorled, isomerous. Calyx 5; more or less polysepalous; regular. Corolla present (in male flowers), or vestigial to absent (in most female flowers); when present, 5; polypetalous; regular. Fertile stamens present, or absent (female flowers). Androecium 5–30. Androecial members free of the perianth; free of one another. Androecium exclusively of fertile stamens. Stamens 5–30; isomerous with the perianth to polystemonous; inflexed in bud. Anthers dehiscing via longitudinal slits; extrorse, or introrse; bisporangiate, or tetrasporangiate. Fertile gynoecium present, or absent (male flowers). Gynoecium 3 carpelled. The pistil 3 celled. Gynoecium syncarpous; synovarious, or synstylovarious; superior. Ovary plurilocular; 3 locular. Styles 3; free, or partially joined (? free or nearly so); forked, or 4-branched; apical. Stigmas 6, or 12; dry type; papillate, or non-papillate; Group II type. Placentation axile, or apical. Ovules 1 per locule; pendulous; epitropous; with ventral raphe, or with dorsal raphe; arillate; anatropous.

Fruit and seed features. Fruit non-fleshy; a schizocarp. Mericarps 3. Fruit elastically dehiscent (schizocarpic capsules often splitting elastically), or passively dehiscent. Seeds 1 per mericarp. Seeds ovoid or ellipsoid; endospermic. Endosperm oily. Seeds arillate. Cotyledons 2 (usually wider than the radicle). Embryo straight, or curved. Testa smooth. Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, biochemistry. Mustard-oils present, or absent.

Geography, cytology, number of species. Native of Australia. Not endemic to Australia. Australian states and territories: Western Australia, Northern Territory, and Queensland. Northern Botanical Province.