Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Spikelets with 1 perfect fl and 1 or more empty lemmas, articulated above the glumes, sessile in 2 rows on 2 sides of a slender triangular rachis; glumes small, unequal, the first 1-veined, the second 1- or 3-veined; lemmas unequal, the lowest fertile, compressed and keeled, usually awned just below the tip, 3-veined, the lateral veins marginal; second lemma smaller, sterile, usually truncate or inflated, awned or awnless; other lemmas, if present, still smaller and mostly concealed within the second; usually tufted, bearing several elongate spikes in a terminal digitate cluster. 40, warm reg.