Description: Annual and perennial herbs, stems terete, glabrous or pubescent.
Leaves cauline, opposite, entire to toothed, sessile and often somewhat joined at the base.
Heads compound, in dense clusters surrounded by leafy general bracts, clusters terminal or sessile in axils; general receptacle minute; partial heads cylindrical or compressed; involucral bracts of partial heads usually 2–5, scarious, subequal; general receptacle minute, naked. Ray florets solitary or absent, female, fertile, ligulate; style branches short, flattened, obtuse. Disc florets 1–15, bisexual, fertile, tubular, 5-toothed; corolla often glandular or hairy; anthers obtuse or subauriculate at base; style branches recurved, flattened, obtuse.
Achenes terete or ± compressed, with 8–10 ribs, glabrous; pappus absent.
Distribution and occurrence: World: c. 16 species, North & South America. Australia: 1 species (native).
Text by L. Murray