1. Schoenus nigricans Linnaeus, Sp. Pl. 1: 43. 1753.
Rhizomes short, oblique. Culms hollow, glabrous. Leaves: basal sheaths blackish, conspicuously wider than leaf blades; blades 10–40 cm × 0.8–2 mm, margins involute, smooth or scabridulous. Inflorescences loosely ovoid, 1–2 cm; bracts 1 or 2, oblique to erect, green to dark brown or black, 1–6 cm × 1–1.5 mm. Spikelets (1–)10–25, flattened, oblong-ellipsoid; rachilla wingless, ± deciduous at maturity; basal scales 2–3, sterile; floral scales 3–8, laterally veinless, medially 1-veined, oblong, apex acute, not mucronate, distally scabrellate. Flowers: perianth bristles 0–6, smooth or scabrellate; anthers linear, connective apices subulate, conspicuous; styles 0.6–1 mm; stigmas 0.5 mm. Achenes whitish, ovoid to ellipsoid, 1–1.5 × 0.9–1.2 mm, glossy, apex obtuse, smooth or barely reticulate. 2n = 54, 55.
Fruiting summer. Damp, calcareous or alkaline grasslands; 0–2000 m; Calif., Fla., Nev., Tex.; Mexico; Eurasia; Africa; Australia.