Heads radiate, the rays pistillate, yellow or white, or rarely wanting and the heads discoid; invol bracts in 1 or 2 series, subherbaceous and subequal; receptacle elongate, conic or subcylindric, its bracts clasping the disk-achenes and eventually deciduous with them; disk-fls perfect and fertile style-branches flattened, truncate, exappendiculate; achenes of the rays 3-angled or tangentially flattened, those of the disk radially flattened, commonly ciliate-margined; pappus of 1-3 slender setiform awns, or none; annual or rarely perennial herbs with opposite, commonly toothed lvs. 40, mainly warm reg.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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