Description from Flora of China
Herbs, annual. Stems erect or ascending. Leaves opposite, petiolate. Capitula radiate, sessile or subsessile, in axillary glomerules or borne singly; involucres cylindric to campanulate; phyllaries persistent, 2-5+, 1(or 2)-seriate; receptacle convex, paleate. Ray florets 1- or 2-seriate, female, fertile; corollas yellowish. Disk florets bisexual, fertile; corollas yellowish, tubes ± equaling slightly ampliate cylindric throats, 4-lobed, orbicular-deltate. Achenes dimorphic, strongly obcompressed or flattened, narrowly oval and winged or linear-cuneate and wingless; pappus of 2 triangular scales (ray) or 2 or 3 subulate scales or awns (disk), persistent.
See Turner, Phytologia 76(1): 39-51. 1994.
One species: Caribbean, Central and South America, Mexico; introduced in Africa, Asia, Australia, and Pacific islands, including China.