Subfamily Sterculioideae), Tribe Sterculieae.
Habit and leaf form. Trees (mostly), or shrubs (usually glabrous, except for the inflorescence); deciduous. To 10–35 m high. Mesophytic. Leaves medium-sized; alternate; petiolate; simple. Leaf blades dorsiventral; dissected, or entire; ovate, or oblong, or elliptic; palmately lobed; cordate, or rounded at the base (or truncate). Mature leaf blades adaxially glabrous, or pubescent (rarely); abaxially glabrous, or pubescent (rarely). Leaves with stipules. Stipules caducous. Leaf blade margins entire. Leaf anatomy. Hairs present, or absent; complex hairs present. Complex hairs peltate.
Reproductive type, pollination. Fertile flowers hermaphrodite, or functionally male, or functionally female. Unisexual flowers present, or absent. Plants hermaphrodite, or monoecious, or polygamodioecious (sometimes). Female flowers with staminodes (10–15 clustered at their base).
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’ (sometimes pendulous). Inflorescence few-flowered (c. 8–12). Flowers in racemes, or in panicles (sometimes). Inflorescences terminal, or axillary. Flowers pedicellate (pedicels sometimes articulate); bracteate. Bracts deciduous. Flowers regular. Floral receptacle developing an androphore, or developing a gynophore (ie. an androgynophore, sometimes minute). Perianth with distinct calyx and corolla; (4–)5. Calyx present; 4, or 5; 1 -whorled; gamosepalous; lobed; lobulate (4- or 5-lobed); erect, or spreading; hairy, or glabrous; campanulate, or urceolate; green, or yellow (ie. green or yellow-green or creamy yellow or yellowish). Epicalyx absent. Corolla absent. Androecium present. Fertile stamens present (in male flowers), or absent (in female flowers). Androecium 10–30. Androecial members coherent (connate); 1 - adelphous (in a column). Androecium exclusively of fertile stamens. Stamens 10–30 (in an irregular globular head at the top of the androgynophore). Anthers dehiscing via longitudinal slits; bilocular. Gynoecium 5 carpelled. The pistil 5 celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary plurilocular; 4 locular, or 5 locular. Gynoecium stylate. Styles 4, or 5 (usually connate); free; hairy. Stigmas 4, or 5; 4 - lobed, or 5 - lobed; peltate. Placentation axile. Ovules 1–5 per locule; anatropous.
Fruit and seed features. Fruit 35–55 mm long; more or less sessile; yellow, or orange, or red, or pink; a schizocarp. Mericarps 3–5; comprising follicles (free, dehiscing longitudinally along the inner suture). Dispersal unit the seed (without a persistent exotesta). Seeds 1 per mericarp, or 2 or more per mericarp (ie. 1–5). Seeds endospermic; medium sized; not conspicuously hairy.
Geography, cytology, number of species. World distribution: tropical. 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 ca 300 species; 2 species in Western Australia; 0 endemic to Western Australia.