Plants annual; rhizomes 1 mm diam. Culms often arching (to decumbent), terete, 0.02–0.5 m × 0.5–1.5 mm. Leaves 1, to equaling culm; sheath fronts not pinnate-fimbrillose; blades 0–1, cross section C-shaped, from a mucro to longer than a sheath by 0.5 mm, smooth. Inflorescences capitate or 1 spikelet; proximal bract erect, very rarely divergent, on longer culms of plants 5–150 mm and 1/5–2/3 culm length. Spikelets 1–15, 5–12 × 3(–4) mm; scales straw-colored to orange-brown, often lineolate-spotted, midrib region usually green becoming straw-colored, obovate, 2.5–3 × 1.5–2 mm, smooth, margins distally ciliolate at 20X, flanks in proximal part of spikelet each with 2–10 distinct ribs, apex rounded, entire, mucronate. Flowers: perianth bristles 0 or 4–6, rarely 1–3, brown, ± equaling to 2 times longer than achene, rarely much shorter, slender throughout, densely to sparsely retrorsely-spreading spinulose; anthers 0.4–0.6 mm; styles 2-fid or 2-fid and 3-fid. Achenes brown, turning blackish, thinly to thickly plano-convex or unequally biconvex, sometimes clearly trigonous with distinct, narrow abaxial angle, adaxial face without central bulge, cuneate-obovoid, proximally evenly tapered and usually without stipelike constriction, 1.5–2 × 1.2–1.5 mm, base 0.2–0.3 mm wide; beak 0.1–0.2 mm, very finely longitudinally ridged at 20–30X.
