The generic circumscription at present includes a S. gracilepes, which is likely to be segregated into a new monotypic genus (B.L.Rye pers. comm.).
Habit and leaf form. Shrubs. ‘Normal’ plants. Leaves well developed. Plants with roots; non-succulent; unarmed; autotrophic. To 1.5 m high. Self supporting, or climbing; scrambling. Not heterophyllous. Leaves small; alternate, or opposite; with blades; leathery; petiolate; simple; not peltate. Leaf blades entire, or dissected (‘bilobed’ in S. bilobum); rolled (‘recurved’); obtriangular (or obcordate); pinnately veined. Mature leaf blades adaxially woolly, or pubescent, or glabrous; abaxially woolly, or pubescent, or glabrous. Leaves with stipules. Stipules scaly; persistent. Leaf blade margins entire; flat. Leaf anatomy. Hairs present, or absent; complex hairs present, or absent. Complex hairs stellate.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’. Inflorescence many-flowered. Flowers in clusters. Inflorescences simple, or compound; terminal; several to many aggregated into dense head-like clusters surrounded by brown bracts and leaves. Flowers pedicellate; bracteate; minute; regular; 5 merous; cyclic; tetracyclic. Free hypanthium present. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present; 5; 1 -whorled; gamosepalous; lobed; hairy, or glabrous; valvate; regular; green, or white, or cream. Calyx lobes ovate. Epicalyx absent. Corolla present; 5; 1 -whorled; alternating with the calyx; polypetalous; regular. Petals clawed, or sessile. Androecium present. Fertile stamens present. Androecial members definite in number. Androecium 5. Androecial members free of the gynoecium; free of one another; 1 -whorled. Stamens 5; all more or less similar in shape; isomerous with the perianth; alternisepalous; filantherous. Anthers separate from one another; dehiscing via longitudinal slits; bilocular; tetrasporangiate. Fertile gynoecium present. Gynoecium 3 carpelled. The pistil 1 celled. Carpels reduced in number relative to the perianth. Gynoecium syncarpous; synstylovarious; inferior, or partly inferior. Ovary plurilocular; 3 locular. Ovary summit glabrous, or hairy, the hairs not confined to radiating bands. Gynoecium stylate. Styles 1; apical. Stigmas 3 - lobed. Ovules 1 per locule (in WA); ascending; anatropous.
Fruit and seed features. Fruit aerial; 1–3.5 mm long; hairy, or not hairy (sometimes becoming so with age); a schizocarp. Dispersal unit the seed, or the fruit. Seeds 1 per locule.
Geography, cytology, number of species. Native of Australia. Endemic to Australia. Australian states and territories: Western Australia and Northern Territory. South-West Botanical Province. A genus of ca 25 species; 21 species in Western Australia; ca 18 endemic to Western Australia.
Etymology. From the Greek for "narrow" and "flower".