Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Fls 4– or 5(–7)-merous; hypanthium not prolonged beyond the summit of the ovary; sep persistent; pet yellow (in our spp.) or white, soon deciduous, or often wanting; stamens as many or twice as many as the sep; ovary cylindric to obconic or prismatic, often angled or winged; style short, with capitate or lobed stigma; ovules numerous; capsule dehiscent longitudinally or by a terminal pore; seeds when pluriseriate in each locule naked and with an evident raphe, when uniseriate surrounded by endocarp from which they may be separated easily or only with difficulty; herbs (ours) or shrubs, mostly of wet places (sometimes aquatic), with alternate or opposite lvs and small or medium-sized diurnal fls sessile or short-pedicellate in the upper axils (in ours) or in terminal spikes or heads. (Jussiaea) 75, mainly trop. Amer.
water primrose, primrose willow