Perennials; glabrous throughout. Rhizomes cylindrical, slender, 0.8-1.5 mm diam. Stems prostrate to decumbent or erect, unbranched or branched, 0.5-4 (-6) dm. Rhizomal leaves absent. Cauline leaves 3-10, usually simple, rarely 3 or 5-foliolate, petiolate; petiolulate or sessile; petiole 0.4-2.5 cm, base not auriculate; lateral leaflets (when present) sessile or petiolulate (to 0.2 cm), blade similar to terminal, considerably smaller; terminal leaflet blade orbicular to reniform or ovate to oblong, 0.4-3 cm × 3-20 mm, (somewhat fleshy), base subcordate to rounded or subtruncate, margins entire or repand, rarely undulate, (apex rounded). Racemes ebracteate. Fruiting pedicels divaricate-ascending to spreading, 0.5-2(-4) mm. Flowers: sepals ovate, 0.7-1.2 × 0.5-0.7 mm, lateral pair not saccate basally; petals absent or rudimentary, to 0.7 mm; filaments 0.5-0.8 mm; anthers ovate, 0.1-0.2 mm. Fruits narrowly oblong to linear, (3-)5-10(-15) × 0.8-1.2 mm; ovules 6-22 per ovary; style 0.2-0.5(-1) mm. Seeds light or yellowish brown, oblong or ovoid, 1-1.4 × 0.7-1 mm.

Flowering Jun-Sep. Tidal marshes, mud flats, tidal shores of rivers, shallow water, swampy areas, shady rocky crevices covered at high tide; 0-10 m; Fla., Maine, Md., Mass., N.J., N.Y., N.C., S.C., Va.