Description from Flora of China
Annuals, perennials, or subshrubs. Stems usually 1, erect or ascending, branched distally or ± throughout. Leaves mostly cauline, opposite, petiolate or sessile; blades usually pinnately 1-3-lobed or undivided, ultimate margin usually entire, both surfaces usually glabrous, sometimes glabrate, hispid, puberulent, or scabridulous. Synflorescence of solitary capitula or corymbose. Capitula radiate, borne singly or in corymbiform arrays; calycular bracts (5-)8, basally connate, ± linear to subulate, herbaceous; involucres hemispheric or subhemispheric, 3-15 mm in diam.; phyllaries persistent, (5-)8, ± 2-seriate, distinct, lanceolate, oblong-lanceolate, ovate-lanceolate, or oblong, ± equal, membranous or herbaceous, margin ± scarious; receptacles flat, paleate; paleae deciduous, linear, flat or slightly concave-convex, scarious or entire. Ray florets neuter; corollas white to pink or purple, or yellow to red-orange. Disk florets bisexual, fertile; corollas yellow or orange, tubes shorter than funnelform throats, lobes 5, ± deltate. Achenes relatively slender, quadrangular-cylindric or -fusiform, sometimes slightly arcuate, attenuate-beaked, wingless [or winged], faces glabrous or hispid to scabridulous or ± setose, sometimes papillate, usually with 1 groove; pappus of 2-4(-8) retrorsely barbed awns, sometimes absent. x = 12.
See Sherff, Publ. Field Mus. Nat. Hist., Bot. Ser. 8(6): 401-447. 1932.
About 26 species: tropical and subtropical America, especially Mexico, widely introduced elsewhere; two species (both introduced) in China.