Annual terrestrial or aquatic herbs. Leaves cauline, appearing rosulate in diminutive plants, sessile; stipules reduced to a connate sheath. Inflorescence of 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-nerved to each lobe, or lateral nerves divided again, to 10-nerved, ±enlarged in fruit. Calyx absent. Corolla 4-lobed, white; lobes valvate. Stamens included. Ovary semi-inferior; ovules many. Styles 2, separate, but sometimes cohering in bud or connate in upper part, withering in fruit. Fruit enclosed in involucre, capsular, persistent, loculicidal; walls membranous; style bases (horns) short, persistent. Seeds angular; testa reticulate or sulcate.
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