Enum. Pl. 2: 142. 1837.
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.
Phenology: Fruiting spring–winter (Apr–Dec).
Habitat: Stream alluvium, lake margins, meadows, seeps, bogs
Elevation: 100–1400 Ariz., Calif., Fla., La., Mich., Okla., Tex., Va.
n Mexico, West Indies, Central America (El Salvador), South America (Argentina), South America (Chile), Pacific Islands (Hawaii)