Herbs. Leaves opposite, without stipules, entire to pinnatifid, often variable on the same plant. Inflorescence usually capitate on a long peduncle, each head surrounded by involucral bracts. Receptacular scales present (in ours). Flowers bisexual, zygomorphic, epigynous, each subtended at its base by an epicalyx (involucel) of united bracteoles. Calyx cup-shaped, sometimes with long spreading bristles. Corolla 4-5-lobed. Stamens exserted, 4 (in ours), anthers free. Ovary inferior, with 1 ovule. Fruit an achene enclosed in the involucel.