Description from Flora of China
Annuals. Leaves cauline, opposite, petiolate or sessile; blade mostly elliptic to deltate, rhombic, or ovate, sometimes lyrate, both surfaces usually pilosulose to sericeous or scaberulose, sometimes glabrescent, usually gland-dotted, ultimate margin entire or toothed. Capitula radiate, 1(-3) in axils of leaves or in forks of branches; involucres hemispheric; phyllaries persistent (outer) or deciduous, 10-13, 2-seriate. Ray florets 5-8, female, fertile; corollas yellowish, tube shorter than to equaling lamina, lamina ovate to elliptic or linear. Disk florets 3-8(-12), functionally male; corollas yellowish, tubes shorter than funnelform or campanulate throats, lobes 5, deltate. Achenes each enclosed within and shed with an often hardened, prickly bur; pappus absent. x = 11.
About six species: mostly tropical to warm-temperate New World; one species (introduced) in China.