Subfamily Alsinoideae, Tribe Alsineae.
Habit and leaf form. Herbs, or shrubs (rarely, subshrubs); non-laticiferous and without coloured juice. ‘Normal’ plants. Leaves well developed. Plants with roots; non-succulent; unarmed. Annual, or perennial. Leaves cauline. To 0.5 m high. Self supporting (or mat-forming). Mesophytic. Not heterophyllous, or heterophyllous (rarely). Leaves variable small to very large; not fasciculate; opposite; with blades; subsessile, or sessile; simple; not peltate. Leaf blades entire; flat; variable. 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. Unisexual flowers absent. Plants hermaphrodite. Floral nectaries 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; small; regular; tetracyclic, or tricyclic (rarely). Free hypanthium present (subperigynous). Perianth with distinct calyx and corolla, or sepaline (rarely); 10, or (4–)5 (rarely); 2 -whorled, or 1 -whorled (rarely); isomerous, or anisomerous (rarely). Calyx present; (4–)5; 1 -whorled; polysepalous; glabrous; valvate. Corolla present, or absent; 0, or 5; 0 -whorled, or 1 -whorled; polypetalous; contorted, or imbricate (rarely); white. Petals emarginate or bifid; sessile. Corolla members deeply bifid, or bilobed (emarginate). Androecium present. Fertile stamens present. Androecium (8–)10, or 5. Androecial members all equal; free of one another; 1 -whorled, or 2 -whorled. Androecium exclusively of fertile stamens. Stamens (8–)10, or 5; isomerous with the perianth, or diplostemonous (obdiplostemonous), or reduced in number relative to the adjacent perianth (rarely); oppositisepalous. Anthers separate from one another; dehiscing via longitudinal slits; introrse; bilocular; tetrasporangiate. Fertile gynoecium present. Gynoecium 1 carpelled. The pistil 1 celled. Gynoecium syncarpous; synovarious; superior. Ovary unilocular; 1 locular. Gynoecium stylate. Styles (2–)5, or 6 (rarely); free; simple. Stigmas (2–)5, or 6 (rarely); 1 - lobed. Placentation free central, or basal. Ovules campylotropous.
Fruit and seed features. Fruit 6–12 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. Not endemic to Australia. Australian states and territories: Western Australia, South Australia, Northern Territory, Queensland, New South Wales, Victoria, Australian Capital Territory, and Tasmania. South-West Botanical Province. 2n=30, 34, 36, 38, 40, 48, 52, 54, 72, 82–86, 90, 94–96, ca 108, ca 126, 144. A genus of ca 100 species; 4 species in Western Australia; 0 endemic to Western Australia.