Bull. Torrey Bot. Club 35: 492. 1908.
Plants densely to loosely cespitose; rhizomes ascending to erect, brown to reddish-brown, 0–10 mm, stout. Culms 4–16 cm, scabrous distally; bases (remnants of old leaves) fibrous. Leaf-blades pale to bright green, equaling or exceeding stems, 0.5–4.3 mm wide, herbaceous or coriaceous, glabrous abaxially, strongly scabrous to papillose adaxially. Inflorescences with both staminate and pistillate scales; peduncles of basal pistillate spikes erect, short-to-elongate, stout to slender; peduncles of staminate spikes 0.8–15 mm; proximal nonbasal bracts scalelike, shorter than inflorescences. Spikes: proximal pistillate spikes 2–3 (basal spikes 1–2); cauline spikes usually overlapping with staminate spikes, with 3–10 (–15) perigynia; staminate spikes 4.5–11.3 × 1.1–3 mm. Scales: pistillate scales pale-brown to reddish-brown, with narrow white margins, ovate, 2.9–4.1 × 1.5–1.9 mm, equaling or exceeding perigynia, apex acute to long-acuminate; staminate scales ovate, 4.2–5.4 × 1.2–2.1 mm, apex obtuse or acute to acuminate. Anthers 1.6–2.9 mm. Perigynia green to pale-brown, veinless, ellipsoid, obtusely trigonous in cross-section, 3.1–4.7 × 1.1–1.6 mm; beak straight, pale green, occasionally with reddish-brown tinge near apex, strongly 2-edged, 0.9–2 mm, smooth or ciliate-serrulate, apical teeth 0.2–0.5 mm. Stigmas 3. Achenes brown, ellipsoid to obovoid, obtusely trigonous in cross-section, 1.6–2 × 1.2–1.6 mm.
Alta., B.C., Man., N.B., N.S., Ont., P.E.I., Que., Sask., Conn., D.C., Ga., Ill., Ind., Maine, Mass., Md., Mich., Minn., N.C., N.H., N.J., N.Y., Ohio, Pa., S.C., Vt., W.Va., Wis.
Varieties 2 (2 in the flora).
|1||Perigynia with few hairs near base of beak, otherwise glabrous; leaves pale green, often relatively short, coriaceous, usually smooth adaxially.||Carex tonsa var. tonsa|
|1||Perigynia pubescent on beak and body; leaves bright green, much longer than culms, herbaceous, scabrous to papillose adaxially.||Carex tonsa var. rugosperma|