Plants perennial, forming small to large mats, from slender rhizomes. Stems trailing to ascending, branched, 4-angled, 10-60 cm, glabrous. Leaves subsessile; blade broadly elliptic to ovate, 0.4-2.6 cm × 2-15 mm, base round to cuneate, margins entire, apex acuminate, glabrous or with a few scattered cilia. Inflorescences with flowers solitary in leaf axils; bracts absent. Pedicels ascending, straight, mostly 5-30 mm, glabrous. Flowers 4-5 mm; sepals 5, prominently 3-veined, lanceolate, 2-4 mm, margins broadly scarious, apex acute to acuminate, glabrous; petals usually absent, rarely 1-5 and much shorter than sepals; stamens 10 or fewer; styles 3, spreading to ascending, curved but not curled, ca. 1 mm. Capsules straw colored or brownish, ovoid to ovoid-ellipsoid, 3.5-6 mm, equaling or slightly exceeding sepals, apex broadly acute, opening by 6 valves; carpophore absent. Seeds brown, broadly elliptic, 0.7-1 mm (longest axis), distinctly rugose. 2n = 26, 52.

Flowering summer. Wet soil in woods, shaded streambanks and shores; 0-2300 m; Alta., B.C.; Alaska, Calif., Idaho, Mont., Oreg., Wash.