Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Tep narrow, lance-subulate to lance-ovate, dry, often firm and even sharp; stamens 6 or 3, opposite the sep when only 3; ovary and fr trilocular, subtrilocular (with incomplete partitions) or unilocular; seeds several to usually numerous (in any case more than 3), commonly ellipsoid or fusiform and minutely apiculate, sometimes with each end prolonged into a slender tail that may be longer than the body; smooth (1 of our spp. scabrous) herbs with usually simple stems and a few flat or terete, basal or cauline lvs, sometimes with bladeless sheaths only, and with a terminal, compact to loosely branched cyme of few–many fls, these solitary, paired, or often in glomerules; lf-sheaths open. 200, cosmop.