Description from Flora of China
Annual or perennial herbs, subshrubs, or shrubs. Stems erect, branched distally or throughout. Leaves cauline, mostly opposite (distal sometimes alternate), petiolate or sessile; blades mostly lanceolate to oblanceolate overall, usually pinnately 1-3-lobed or ‑pinnatisect, ultimate margin toothed or entire, both surfaces glabrous or hairy. Synflorescence of solitary capitula or of sometimes dense, many-headed corymbs. Capitula radiate or discoid; calyculus absent; involucres narrowly cylindric or fusiform to turbinate or broadly campanulate, 1-12+ mm in diam.; phyllaries persistent, 1- or 2-seriate (connate to 7/8+ their lengths, usually streaked and/or dotted with oil glands); receptacle convex to conical, smooth or finely pitted, epaleate. Ray florets female, fertile (except "double" cultivars); lamina yellow or orange, red-brown, or white. Disk florets bisexual, fertile; corollas greenish yellow to orange, sometimes tipped with red or red-brown, tubes much longer than or ± equaling funnelform throats, lobes 5, deltate to linear-lanceolate. Achenes narrowly obpyramidal or fusiform-terete, sometimes weakly flattened, glabrous or hairy; pappus persistent, of 2-5(-10) dissimilar, distinct or connate, 1-seriate scales: 0-5+ oblong to lanceolate, erose-truncate or laciniate, 0-2(-5) longer, subulate to aristate. x = 12.
About 40 species: tropical and warm-temperate America, especially Mexico; two species (both introduced) in China.