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 sterile vestiges, articulated above the glumes, inserted in 2 rows on one side of a narrow flat rachis; glumes unequal, narrow, 1-veined, acuminate to awn-pointed; fertile lemma rounded on the back, 3-veined, the lateral veins marginal or submarginal, usually excurrent below the tip into a short awn; vestige stipitate, reduced to an empty 3-awned lemma; usually tufted, the relatively short spikes 1–many, racemose on a common axis. 40, New World.