Very much like no. 228 [Carex lupulina Willd.]; perigynia ascending to spreading; achene 3-4.5 נ2.4-3.4 mm, its faces strongly concave, diamond-shaped in outline, each lateral angle straight-tapering to each end from a hard, nipple-like knob near the middle; 2n=60. Wetter places than no. 228, in open marshes or along shores, sometimes in shallow water, or in very wet floodplain forests; Vt. and adj. Que. to Minn., s. to Va., Ky., and Tex.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.