Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Spikelets in pairs, one perfect, sessile, and subterete, the other represented only by its pedicel (2 such pedicels flanking the terminal spikelet of a raceme); glumes coriaceous, the first one hirsute, clasping or enclosing the glabrous or ciliate second one; lemmas 2, small, thin and hyaline, the lower one empty (sometimes nearly obsolete), the upper fertile and ending in a bent, twisted awn; erect perennials with elongate blades tapering to the base, the sheaths auricled at the summit; panicle slender, its ultimate branches bearing short, disarticulating racemes of 1–5 pairs of spikelets. 12, warm Amer. and Afr.