Annual terrestrial or aquatic herbs. Leaves cauline, widely spaced (in Victorian species), appearing rosulate in diminutive plants, sessile; stipules reduced to a connate sheath. Inflorescence with solitary peduncles or peduncles several to many in umbellate clusters; flowers solitary (rarely 2), very shortly pedicellate, enclosed in a 2-lobed foliaceous involucre; involucre 3-veined to each lobe, or lateral veins divided again, to 10-veined, often enlarged in fruit. Calyx absent; corolla 4-lobed, white, lobes valvate; stamens included; ovary semi-inferior, ovules many, styles 2, one on each locule, separate, sometimes cohering in bud or connate in upper part. Fruit enclosed in involucre, capsular, persistent, loculicidal, walls membranous; seeds angular; testa reticulate or sulcate.
5 species, all endemic to temperate Australia.