Tridax L.

Annual or perennial, erect, procumbent or decumbent herbs; stems rooting at nodes when prostrate, usually hairy, glandular. Leaves opposite, sessile or petiolate, simple, toothed (Australian sp.; trilobed or pinnately lobed elsewhere). Capitula discoid or radiate, terminal, solitary, rarely in cymose panicles, hemispherical to campanulate, on long naked peduncles; involucral bracts 2-or 3-seriate; outer bracts herbaceous; inner bracts membranous, often transitional to paleae; receptacle conical or convex; paleae scarious, persistent, partially enclosing achenes. Ray florets few in 1 row, female, fertile; ligules usually 3-lobed. Disc florets numerous, bisexual, fertile, 5-lobed. Achenes turbinate, narrowly obconical or subcylindrical, glabrous to densely pilose. Pappus of numerous plumose bristles or scales, that of ray achenes often reduced, rarely absent.