Family Papilionaceae. Bossiaeae.
Habit and leaf form. (Sub) shrubs. To 0.2–0.6 m high. Xerophytic. Leaves small to medium-sized (7–27 mm long); alternate; ‘herbaceous’, or leathery; not imbricate; petiolate; non-sheathing; compound; pulvinate; unifoliolate. Leaflets 1; (6–)10–20(–27) cm long; not stipellate; pulvinate; elliptic, or linear; flat, or folded. Leaf blades dorsiventral. Leaves with stipules. Stipules intrapetiolar; free of one another; small; persistent. 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.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’ (usually); in racemes. Inflorescences simple. The terminal inflorescence unit racemose. Inflorescences terminal, or leaf-opposed; terminal, pedunculate racemes. Flowers pedicellate, or subsessile; bracteate (the bracts small); bracteolate (but no series of subtending scales). Bracteoles small, on the pedicel. Bracteoles not adnate to the receptacle. Flowers minute to medium-sized; very irregular; zygomorphic; not resupinate. The floral asymmetry involving the perianth. Flowers papilionaceous (imbricate-descending, with the posterior petal outside and forming a flag (‘standard’)); basically 5 merous. Floral receptacle developing a gynophore. Free hypanthium present (as long as the calyx tube). Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present; 5; 1 -whorled; gamosepalous; (5) lobed. Calyx lobes about the same length as the tube. Calyx imbricate, or valvate; exceeded by the corolla; bilabiate (the posterior pair of lobes more joined); non-fleshy; persistent; with the median member anterior. Epicalyx absent. Corolla present; 5; 1 -whorled; appendiculate (the wing and keel petals auriculate). Standard not appendaged. Corolla partially gamopetalous. 2 of the petals joined (the two ventral petals connivent to form the ‘keel’?). The joined petals of the papilionate corolla anterior. The wings of the corolla free from the keel; auriculate. Standard ‘normally’ developed; entire to emarginate (nearly circular); not sericeous. Keel conspicuously exceeded by the wings, or about equalling the wings; not long-acuminate/beaked; neither coiled nor spiralled; not bent and beaked. Corolla imbricate (descending); plain, or with contrasting markings (then with purple or brown markings); yellow, or yellow and purple, or yellow and brown; deciduous. Petals clawed. Androecial members definite in number. Androecium 10. Androecial sequence determinable, or not determinable. Androecial members free of the perianth; markedly unequal (alternately longer and shorter, at least in bud); coherent (into an adaxially split sheath); 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; dimorphic to all alike (‘obscurely dimorphic’, with conspicuous connectives); all dorsifixed (but alternate filaments inserted a little higher); versatile; dehiscing via longitudinal slits; latrorse, or introrse; tetrasporangiate. Pollen shed as single grains. 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-) curved (from the base). Style terete. Style glabrous. Stigmatic tissue terminal. Carpel 6–8 ovuled. Placentation marginal (along the ventral suture). Gynoecium median (the placenta posterior, on the ventral suture). Ovary stipitate. Ovules pendulous to ascending; biseriate; arillate (the aril small, white, hooded); anatropous, or campylotropous to amphitropous, or hemianatropous.
Fruit and seed features. Fruit aerial; 15–17 mm long; stipitate; non-fleshy; hairy, or not hairy; not spinose. The fruiting carpel dehiscent; a legume. Pods much elongated (narrow); not triangular; more or less straight; not becoming inflated; more or less flat; not constricted between the seeds; not transversely septate; wingless (and not margined). Valves of the dehisced pod twisted, or not twisted. Fruit 1 celled; elastically dehiscent, or passively dehiscent. Dispersal unit the seed. Fruit 1–4(–7) seeded. Seeds not lobed; endospermic, or non-endospermic; not mucous; compressed, or not compressed; small; arillate (the aril small, white, hooded). Cotyledons 2; accumbent. Embryo curved to bent (the radicle inflexed). Testa non-operculate. Micropyle zigzag, or not zigzag.
Physiology, biochemistry. Aluminium accumulation not found. Photosynthetic pathway: C3.
Geography, cytology, number of species. Native of Australia. Endemic to Australia. Australian states and territories: Western Australia and Northern Territory. Eremaean Botanical Province. A genus of 1 species; 1 species in Western Australia.