Hypanthium ellipsoid to turbinate or campanulate, permanently enclosing the ovary or ovaries; sep mostly 4, spreading or ascending; bractlets sometimes present; pet none; stamens 4(5), inserted on the outer margin of the disk; pistil commonly 1(2-3); style basal; fr an achene; rhizomatous perennial herbs with small clusters of fls arranged in openly branched, cymose infls. 100+, widespread.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.