Annual, biennial or perennial herbs, rarely woody at base. Leaves opposite, connected across node by a ridge, simple, entire, dentate or lobed, sessile or petiolate. Inflorescences depressed subglobose or ovoid-conical; involucral bracts in 1–3 rows, non-spinose, persistent; receptacle bracts usually linear-lanceolate; epicalyx cylindrical, ribbed, with a cupular corona. Calyx with 5 bristle-like lobes covered with fine hairs and stalked glands, persistent in fruit; corolla funnel-shaped with a short tube and 5 unequal lobes in marginal flowers, lobes subequal and shorter in central flowers; stamens 4, anthers exserted, versatile; stigma 2-lobed. Fruit an ellipsoid cypsela.