Plants annual or perennial, forming mats, rhizomatous. Stems creeping, much-branched, rooting at lower nodes, 4-angled, 5-30 cm, glabrous or sparsely pubescent on 2 sides. Leaves sessile to subsessile; blade elliptic to obovate, 0.3-1.5 cm × 1-6 mm, base cuneate to spatulate, margins entire, apex obtuse to ± acute, tip blunt, glabrous or pubescent at base and stem nodes. Inflorescences with flowers solitary, axillary in distal nodes; bracts absent. Pedicels spreading, becoming reflexed in fruit, 2-10 mm, glandular-pubescent. Flowers 3-4 mm diam.; sepals 4-5, herbaceous with midrib, ovate-lanceolate, 2.5-3 mm, margins convex, membranous, apex obtuse, glandular-pubescent; petals 4-5, ca. 3 mm, equaling sepals; stamens 4-5; styles 3-4, ascending. Capsules broadly ovoid, ca. 4.5 mm, longer than sepals, apex obtuse, opening by 6-8 valves; carpophore absent. Seeds ca. 20, brown, round, ca. 1 mm diam., prominently papillate; papillae obtuse, taller than broad. 2n = 34. Flowering spring-fall. Short grass in ditches and marshy areas; less than 100 m; introduced; La., Tex.; South America (Argentina, Brazil, Paraguay).