Annual or perennial herbs to subshrubs, scram- bling shrubs or small trees, without latex; leaves opposite or alternate; heads discoid, varying in size; involucre cam- panulate to cylindrical, bracts persistent to totally decidu- ous; receptacle often conical, with or without hairs, rarely with simple paleae; florets one to many in a head, corollas white to reddish, blue or lavender, actinomorphic (rarely peripheral florets with outer one or three lobes enlarged, 4- or 5-lobed); anthers often with glands, with apical ap- pendages hollow, reduced or lacking, thecae not spurred or tailed; style branches spreading radially (not in some Praxelinae), apical appendages not recurving, greatly en- larged, filiform, flattened or fusiform, often colored as in corolla, usually nearly smooth; achenes 4–10-ribbed with phytomelanin in walls, without raphids, usually with twin hairs; pappus usually uniseriate, of plumose bristles, scales or lacking; pollen spherical, echinate, mostly 18–25 μm in diam. (in medium), caveate.
All members of the tribe (with a few exceptions) have mono-ester type pyrrolizidine alkaloids secreted by nectaries; also with pentaynene acetylenes, some monoterpenes and sesquiterpene lac- tones, an ent-kaurine diterpene glycoside, kolavane de- rivatives, chromenes, benzofurans; raphids in the achenes are completely lacking. Other diagnostic features: mostly opposite leaves; hairs simple; heads discoid; corollas ac- tinomorphic and whitish to reddish or lavender (never yellow); anther appendages hollow or poorly developed; and style branches with enlarged “club shaped” append- ages that are often the color of the corolla.
Western Hemisphere with a few pantropical genera.