Subfamily Alsinoideae, Tribe Alsineae.
Habit and leaf form. Herbs; non-laticiferous and without coloured juice. ‘Normal’ plants. Leaves well developed. Plants with roots; non-succulent; unarmed. Annual, or perennial. Leaves basal and cauline. To 0.59–1.35 m high. Self supporting. Mesophytic. Not heterophyllous. Leaves small to medium-sized; not fasciculate; opposite; with blades; sessile, or petiolate; simple; not peltate. Leaf blades entire; flat. Mature leaf blades adaxially glabrous; abaxially glabrous. Leaves without stipules. Leaf blade margins entire; flat. Leaf anatomy. Hairs absent; glandular hairs absent.
Reproductive type, pollination. Fertile flowers hermaphrodite, or functionally male (rarely), or functionally female (rarely). Unisexual flowers absent, or present (rarely). Plants hermaphrodite, or gynodioecious (rarely). Floral nectaries absent, or present.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’, or solitary (rarely). Inflorescence few-flowered. Flowers in cymes. Inflorescences compound. The terminal inflorescence unit cymose. Inflorescences terminal. Flowers pedicellate; bracteate. Bracts scarious or herbaceous. Flowers small; regular; tetracyclic, or tricyclic. Free hypanthium present (subperigynous), or absent. Perianth with distinct calyx and corolla; 8–10, or 5; 2 -whorled, or 1 -whorled (rarely); isomerous, or anisomerous (rarely). Calyx present; 4 (rarely), or 5; 1 -whorled; polysepalous; glabrous; valvate. Corolla present, or absent; 0 (rarely), or 4, or 5; 1 -whorled, or 0 -whorled; polypetalous; contorted, or imbricate (rarely); white, or green (rarely). Petals deeply bifid; sessile. Corolla members deeply bifid. Androecium present, or absent. Fertile stamens present. Androecial members definite in number. Androecium (3–)5–10, or 11 (rarely). Androecial members all equal; free of one another; 1 -whorled, or 2 -whorled. Androecium exclusively of fertile stamens. Stamens (3–)5–10, or 11 (rarely); isomerous with the perianth, or diplostemonous (obdiplostemonous), or reduced in number relative to the adjacent perianth (rarely). Anthers separate from one another; dehiscing via longitudinal slits; introrse; bilocular; tetrasporangiate. Fertile gynoecium present, or absent. Gynoecium 1 carpelled. The pistil 1 celled. Gynoecium syncarpous; synovarious; superior. Ovary unilocular; 1 locular. Gynoecium stylate. Styles 2 (rarely), or 3, or 4–5 (rarely); free; simple. Stigmas 2 (rarely), or 3, or 4–5 (rarely); 1 - lobed. Placentation free central, or basal. Ovules campylotropous.
Fruit and seed features. Fruit ca 6 mm long; not hairy; dehiscent; a capsule. Dispersal unit the seed. Fruit 50 seeded (‘numerous’). Perisperm present. Seeds minute, or small.
Geography, cytology, number of species. Holarctic. Adventive, or native of Australia. Not endemic to Australia. Australian states and territories: Western Australia, South Australia, Northern Territory, Queensland, New South Wales, Victoria, Australian Capital Territory, and Tasmania. 2n=20, 22, 24, 26, 28, 30, 36, 40, 42, 44, 46, 52, 60, 65, 72, 78, 84, 90, 91, 104, ca 130, 174–188. A genus of 150–200 species; 3 species in Western Australia; 0 endemic to Western Australia.