Plants annual, cespitose or solitary, (10-)20-100 cm; rhizomes absent. Culms erect, leafy, nearly terete or angled, many ribbed. Principal midculm leaves often exceeding inflorescences; blades linear, proximally flattened, 1-5 mm wide, apex trigonous, tapering. Inflorescences terminal and axillary, clusters of corymbs 1-5, usually diffuse; leafy bracts exceeding proximal corymbs. Spikelets dark brown, lanceoloid to ovoid, mostly 4-6(-8) mm, apex acute; fertile scales many, ovate, rounded-convex, 2-3.5 mm, apex acute, midrib mostly included, rarely forming apiculus. Flowers: perianth absent. Fruits 1-1.3(-1.5) mm, body dark brown, tumidly lenticular, nearly orbicular, 0.7-1 × 0.7-1 mm, margins strong, interrupted at tubercle base; surfaces irregularly transversely rugulose with wavy rows of vertical, linear, raised cells; tubercle depressed-triangular, 0.1-0.3 mm, capping fruit summit, base broadly 2 lobed. Fruiting summer-fall or all year. Moist to wet sands or peats of stream banks, pond shores, depressions in savannas, marshes; 0-100 m; Ala., Del., Fla., Ga., Ind., La., Mass., Mich., Miss., N.J., N.Y., N.C., S.C., Tex., Va.; West Indies; Central America.