Plants perennial, mat-forming; rhizomes 0.2-0.5 mm thick, longer internodes 5-10 mm, scales not evident. Culms obscurely to ca. 10-ribbed when dry, terete, 1-12 cm × 0.4-1 mm, very soft, spongy. Leaves: distal leaf sheaths fugaceous, colorless, translucent, apex blunt. Spikelets ovoid, 2-3 × 1-1.5 mm, apex acute; scales 5-15, 5-7 per mm of rachilla, colorless to stramineous, rarely slightly reddish, medially broadly greenish to colorless, faintly 3-5-veined, often ovate, membranous, fleshy; proximal scale 2-2.5 × 0.7 mm, other scales 1.5-2 × 0.7 mm, midrib obscure to slightly keeled, apex acute to rounded. Flowers: perianth bristles equaling achene; anthers yellow to brown, 0.3-0.5 mm. Achenes brownish, angles plus longitudinal ridges ca. 7, narrowly obovoid, 2 times longer than wide, 0.75-0.9 × 0.35-0.4 mm, trabeculae ca. 50, distinct. Tubercles brown, pyramidal, 0.15 × 0.15-0.2 mm. Fruiting spring-winter (Apr-Dec). Stream alluvium, lake margins, meadows, seeps, bogs; 100-1400 Ariz., Calif., Fla., La., Mich., Okla., Tex., Va.; n Mexico; West Indies; Central America (El Salvador); South America (Argentina, Chile); Pacific Islands (Hawaii).