Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Sep oblong, obtuse; pet white, spatulate, gradually narrowed to the base; filaments capillary; anthers ovate; short stamens subtended by a minute semicircular gland; each pair of long stamens separated by a minute gland; ovary cylindric, ovules numerous; style undifferentiated; stigma truncate; fr linear, subterete, the valves with conspicuous midnerve, the cells of the septum vertically elongate, herbs, ± pubescent with branched hairs. 15, N. Hemisphere.