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Heads radiate, the rays few, short and rather inconspicuous, white or yellowish, pistillate and fertile, the expanded part rarely wanting and the heads thus disciform; invol of 2–4 series of broad, ± imbricate, dry and scarcely herbaceous bracts, the inner subtending the rays; receptacle small, convex or conic, chaffy; disk-fls staminate, with undivided style; ray-achenes flattened parallel to the invol bracts, their subtending bracts joined at base to the 2 or 3 adjacent receptacular bracts, thus partly enclosing the achene, the whole commonly falling as a unit; pappus of 2 or 3 short or elongate awns or scales, or nearly obsolete; bitter, aromatic herbs (ours) or shrubs with alternate, entire to pinnatifid lvs and rather small hemispheric heads. 16, New World.
Herbs or shrubs. Leaves alternate. Capitula in terminal panicles, radiate, heterogamous; involucre with phyllaries in 2–3 series; receptacle paleate. Female florets with minute rays; disc florets infundibuliform; anthers with apical appendage, obtuse at base; style of ray florets bifid, of disc florets entire and obtuse. Achenes of ray florets compressed, keeled, enveloped by phyllary and two paleae; pappus of 2 recurved awns enclosed in the paleae.
