Family Papilionaceae. Crotalarieae.
Habit and leaf form. Diffuse or trailing herbs. Annual; plants with neither basal nor terminal concentrations of leaves; to 0.3–3 m high. Mesophytic, or xerophytic. Leaves minute to very large; alternate; spiral, or distichous; not imbricate; petiolate to subsessile (usually), or sessile; non-sheathing; compound; pulvinate; ternate. Leaves palmately trifoliolate. Leaflets 3; not stipellate; pulvinate, or epulvinate. Leaf blades dorsiventral, or isobilateral, or centric. Leaves with stipules. Stipules intrapetiolar; free of the petiole; free of one another; caducous, or persistent. Leaves without a persistent basal meristem. Leaf anatomy. Hairs present; glandular hairs absent; complex hairs absent. Branched hairs absent. Stem anatomy. Nodes tri-lacunar, or penta-lacunar. Secondary thickening absent, or developing from a conventional cambial ring.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’ (usually), or solitary; when aggregated, in racemes (the racemes short, 1–5 flowered). Inflorescences simple. The terminal inflorescence unit racemose. Inflorescences leaf-opposed (‘really’ terminal). Flowers bracteate (bracts setaceous); bracteolate (the bracteoles setaceous). Bracteoles usually persistent. Bracteoles adnate to the receptacle to not adnate to the receptacle. Flowers minute to small; very irregular; zygomorphic. The floral asymmetry involving the perianth, or involving the perianth and involving the androecium. Flowers papilionaceous (imbricate-descending, with the posterior petal outside and forming a flag (‘standard’)); basically 5 merous. Floral receptacle with neither androphore nor gynophore; usually more or less cupular. Free hypanthium present, or absent. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present; 5; 1 -whorled; gamosepalous; five lobed; imbricate, or valvate; somewhat bilabiate (the lobes subequal and narrow, but the posterior pair broader and falcate); persistent; with the median member anterior. Corolla present; 5; 1 -whorled; appendiculate, or not appendiculate. Standard not appendaged. Corolla polypetalous to partially gamopetalous (the two ventral ‘keel’ petals similar to the wings and scarcely connivent). 2 of the petals joined. The joined petals anterior. The wings of the corolla free from the keel; not laterally spurred. Standard ‘normally’ developed (but small, ovate or oblong); not sericeous. Keel about equalling the wings; not long-acuminate/beaked (blunt); neither coiled nor spiralled; not bent and beaked. Corolla imbricate (descending); pink. Androecial members definite in number. Androecium 10. Androecial sequence not determinable. Androecial members free of the perianth; all equal, or markedly unequal; coherent (the filaments united basally into an adaxially split tube); 1 - adelphous. The staminal tube free from the keel petals. Androecial members 1 -whorled (even though diplostemonous). Androecium exclusively of fertile stamens. Stamens 10; all more or less similar in shape; diplostemonous; both opposite and alternating with the corolla members. Anthers separate from one another, or connivent; all alike (all small); dorsifixed; versatile; dehiscing via pores, or dehiscing via longitudinal slits; latrorse, or introrse; tetrasporangiate. Gynoecium 1 carpelled. The pistil 1 celled. Carpels reduced in number relative to the perianth. Gynoecium monomerous; of one carpel; superior. Carpel stylate; apically stigmatic. Style straight. Style glabrous. Stigmatic tissue terminal. Carpel 12–50 ovuled (i.e. to ‘many’). Placentation marginal (along the ventral suture). Gynoecium median (the placenta posterior, on the ventral suture). Ovary sessile. Ovules pendulous to ascending; biseriate; arillate, or non-arillate; anatropous, or campylotropous to amphitropous, or hemianatropous.
Fruit and seed features. Fruit sessile; non-fleshy; hairy, or not hairy. The fruiting carpel dehiscent; a legume. Pods much elongated (linear or linear-lanceolate); not triangular; straight; beaked; not becoming inflated; more or less flat, or somewhat compressed; not transversely septate; wingless. Fruit 1 celled; passively dehiscent (when mature, gaping along the adaxial suture). Dispersal unit the seed. Fruit 2–50 seeded (to ‘many’). Seeds endospermic, or non-endospermic; not mucous; small; non-arillate. Cotyledons 2; accumbent. Embryo chlorophyllous; curved to bent (the radicle incurved). Testa non-operculate. Micropyle zigzag, or not zigzag. Seedling. Germination phanerocotylar.
Physiology, biochemistry. Nitrogen-fixing root nodules present. Aluminium accumulation not found. Photosynthetic pathway: C3.
Geography, cytology, number of species. Native of Australia. Not endemic to Australia. Australian states and territories: Western Australia and Northern Territory. 2n= 14. A genus of 2 species; 1 species in Western Australia.