(Subfamily Byttnerioideae), Tribe Helictereteae.
Habit and leaf form. Shrubs, or trees; non-laticiferous and without coloured juice. ‘Normal’ plants. Leaves well developed. Plants with roots; non-succulent. Leaves cauline. To 1–3 m high. Self supporting. Mesophytic. Not heterophyllous. Leaves small, or medium-sized; alternate; distichous; with blades; petiolate. Petioles wingless. Leaves with ‘normal’ orientation; simple; not peltate. Leaf blades neither inverted nor twisted through 90 degrees; dorsiventral; entire; flat; ovate, or oblong, or elliptic; pinnately veined; cross-venulate; oblique at the base, or cordate. Mature leaf blades adaxially pubescent (to sparsely so), or glabrous; abaxially pubescent. Leaves with stipules. Stipules intrapetiolar; free of the petiole; free of one another; spiny; caducous (in Australian species). Leaf blade margins entire, or serrate. Leaf anatomy. Hairs present; complex hairs present. Branched hairs present. Complex hairs stellate.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Plants homostylous. Floral nectaries absent.
Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’; not crowded at the stem bases; terminal, or axillary; in cymes (or clusters). Inflorescences simple; terminal, or axillary. Flowers ebracteate; bracteolate; small; regular, or somewhat irregular (usually); zygomorphic; not resupinate. The floral asymmetry involving the perianth. Flowers neither papilionaceous or pseudo-papilionaceous; 5 merous; cyclic; tetracyclic. Floral receptacle developing an androphore and developing a gynophore (as a long ‘androgynophore’). Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present; 5; 1 -whorled; gamosepalous; lobed. Calyx lobes markedly shorter than the tube. Calyx hairy (densely stellate hairy); valvate; exceeded by the corolla; bilabiate (usually slightly so); neither appendaged nor spurred. Epicalyx absent. Corolla present; 5; 1 -whorled; appendiculate (or winged usually at apex of claw), or not appendiculate; polypetalous; contorted; hairy abaxially (sparsely), or glabrous abaxially; hairy adaxially, or glabrous adaxially; yellow, or pink, or purple. Androecium present. Fertile stamens present. Androecial members definite in number. Androecium 10–15. Androecial members free of the perianth; free of the gynoecium; markedly unequal; coherent (connate into a staminal tube, staminodes alternating with 1 or 2 stamens, or inside the staminal tube); 1 - adelphous (stamens only); 2 -whorled. Androecium including staminodes. Staminodes 5; non-petaloid. Stamens 5, or 10; all more or less similar in shape; isomerous with the perianth, or diplostemonous; filantherous. Anthers separate from one another; all alike; dehiscing via longitudinal slits; bilocular. Fertile gynoecium present. Gynoecium 5 carpelled. The pistil 5 celled. Carpels isomerous with the perianth. Gynoecium syncarpous; synovarious, or synstylovarious, or eu-syncarpous; superior. Ovary plurilocular; 5 locular; subsessile. Gynoecium stylate. Styles 1, or 5; free, or partially joined; simple; apical. Stigmas 1, or 5; 1 - lobed, or 5 - lobed; subulate. Placentation axile. Ovules 4–50 per locule (‘several to many’).
Fruit and seed features. Fruit 7–20 mm long; dehiscent. Dispersal unit the seed. Fruit 50 seeded (‘numerous’). Seeds small.
Geography, cytology, number of species. Native of Australia. Endemic to Australia. Australian states and territories: Western Australia, Northern Territory, and Queensland. Northern Botanical Province. A genus of ca 60 species; 3 species in Western Australia; 1 endemic to Western Australia.
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Western Australian Herbarium (1998–). FloraBase—the Western Australian Flora. Department of Biodiversity, Conservation and Attractions. https://florabase.dpaw.wa.gov.au/