Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Fls polygamous; tep 6, free from the ovary, narrowed at base, not glandular; stamens 6; filaments slender, free or adnate to the perianth at the very base; anthers extrorse, obcordate, with confluent thecae; ovary superior, 3-lobed, each lobe terminated by a short style; capsule ovoid, septicidal, subtended by the withered perianth; seeds large, flat, the small embryo surrounded by a broad wing; tall, coarse, poisonous herbs, perennial from a stout rhizome, with large broad lvs and a terminal panicle of green or purple fls. 30, N. Hemisphere.