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 to rotund; pet small, white (yellow), linear to spatulate, or often lacking; stamens 6, or by abortion 4 or 2; anthers small, oval; ovary flat; ovules 1 per locule, suspended; style short or none; stigma capitate; fr a silicle, flattened contrary to the narrow septum, thin or somewhat distended over the seeds, ovate to orbicular or obovate, often winged, commonly retuse, tipped by the persistent style or stigma; herbs with linear to elliptic, entire to pinnatifid lvs. 175, cosmop.