Family Papilionaceae. Desmodieae.
Habit and leaf form. Shrubs, or herbs (erect or prostrate, with hooked hairs). Plants unarmed. Perennial. Leaves cauline. Plants with neither basal nor terminal concentrations of leaves; to 0.2–0.6 m high (in ours). Mesophytic, or xerophytic. Leaves small to large; not fasciculate; alternate; spiral; ‘herbaceous’, or leathery; not imbricate; petiolate. Petioles wingless. Leaves non-sheathing; compound; pulvinate; unifoliolate. Leaflets 1; stipellate; pulvinate, or epulvinate; flat, or folded; without lateral lobes. Leaf blades dorsiventral; cross-venulate. Leaves with stipules. Stipules intrapetiolar; free of one another; scaly (striate, scarious); persistent. Leaf blade margins entire; flat. Leaves without a persistent basal meristem. 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, or ornithophilous.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in pairs, subtended by a common bract; in racemes. Inflorescences compound (2 flowers per node); terminal, or axillary, or leaf-opposed. Flowers pedicellate; bracteate. Bracts deciduous (caducous). Flowers ebracteolate; small; very irregular; zygomorphic; not resupinate. 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 the ‘standard’); basically 5 merous. Floral receptacle developing a gynophore (short), or with neither androphore nor gynophore. Free hypanthium present, or absent. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present; 5; 1 -whorled; gamosepalous (glumaceous, striate); 5 lobed (with strong nerves proliferating from the bases of the lobes). Calyx lobes markedly longer than the tube. Calyx imbricate, or valvate; exceeded by the corolla; bilabiate (the posterior pair of members connate for all or much of their length); non-fleshy; persistent; non-accrescent (but enclosing the fruit); with the median member anterior. Epicalyx absent. Corolla present; 5; 1 -whorled; appendiculate (the keel petals auriculate). Standard not appendaged. Corolla partially gamopetalous. 4 of the petals joined (the two ventral petals connivent cohering to form the ‘keel’, and the wings more or less adhering to the keel). The joined petals of the papilionate corolla anterior (and lateral). The wings of the corolla adherent to the keel; not laterally spurred. Standard ‘normally’ developed; not sericeous. Keel about equalling the wings; not long-acuminate/beaked; neither coiled nor spiralled; not bent and beaked. Corolla imbricate (descending); yellow, or orange, or red to purple (or in combinations); deciduous; non-accrescent. Petals clawed (wings and keel, the standard sessile). Androecial members definite in number. Androecium 10. Androecial sequence determinable, or not determinable. Androecial members free of the perianth; markedly unequal (the filaments alternately long and short); coherent (basally, into a split tube); 2 - adelphous (the vexillary stamen free). The staminal tube free from the keel petals. Androecial members 1 -whorled (although 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; dorsifixed; versatile; dehiscing via longitudinal slits; latrorse, or introrse; tetrasporangiate. Pollen shed as single grains (tricolporate). Fertile gynoecium present. 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 (in-) bent (geniculate). Style glabrous. Stigmatic tissue terminal. Carpel 4–15 ovuled (‘several’). Placentation marginal. Gynoecium median (the placenta posterior, on the ventral suture). Ovary shortly stipitate. Stigmas capitate. Ovules pendulous to ascending; biseriate; arillate, or non-arillate; anatropous, or campylotropous to amphitropous, or hemianatropous.
Fruit and seed features. Fruit shortly stipitate, or subsessile, or sessile; non-fleshy; hairy, or not hairy; not spinose. The fruiting carpel indehiscent; a loment. Pods much elongated (exserted from calyx); not triangular; straight, or curved; becoming inflated to not becoming inflated; somewhat compressed, or terete; regularly constricted between adjacent seeds, or not constricted between the seeds; transversely septate between the seeds, or not transversely septate; wingless. Fruit 1 celled; (1–)2(–3) seeded. Seeds ellipsoid to oblong or rhomboid; endospermic, or non-endospermic; not mucous; compressed; small; non-arillate. Cotyledons 2; accumbent. Embryo curved, or bent (the radicle inflexed). Testa non-operculate. Micropyle zigzag, or not zigzag. Seedling. Germination phanerocotylar, or cryptocotylar.
Physiology, biochemistry. Nitrogen-fixing root nodules present. Aluminium accumulation not found. Photosynthetic pathway: C3.
Geography, cytology, number of species. Native of Australia and adventive. Not endemic to Australia. 2n=16, 20. A genus of 1 species; 7 species in Western Australia.
Additional comments. According to Polhill & Raven (1981) all but one species belong in Desmodium, but local authors ignore this.