Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Sep 3–5, obovate, petaloid, caducous; pet 4–10, deciduous, spatulate to obovate, clawed; stamens numerous, the elongate filaments mostly widened upwards; anthers oval; pistil 1; stigma broad, sessile, bilobed; fr 1- to several-seeded berry; poisonous, odoriferous perennial herbs with large, ternately 2–3 times compound lvs, sharply toothed lfls, and small, white fls in a dense, long-peduncled, terminal raceme. 5, circumboreal.