Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Sep erect or spreading, the outer sometimes saccate at base; pet white, yellowish, or pink, narrowly spatulate to oblong or obovate; anthers oblong; ovary cylindric; ovules numerous; style short and scarcely differentiated; stigma truncate; fr linear, elongate, flat or subterete, the valves often with a midvein or reticulately veined; seeds flattened, often winged; annual to perennial herbs, the basal lvs petioled, usually simple, the cauline smaller and usually sessile; pubescence variable but usually present. 180, N. Hemisphere.