Annual, biennial or perennial herbs; stems erect, terete, striate. Leaves basal and cauline, alternate, pinnatifid. Capitula ovoid or globose, terminal, solitary, pedunculate; involucral bracts in several series, unequal, imbricate, coriaceous, with a short erect to reflexed deciduous terminal spine; receptacle concave, scales present. Florets tubular, purple, rarely white; outer florets sterile, staminodes present; inner florets bisexual; corolla deeply 5-lobed; anthers caudate at base; style bilobed, with linear erect branches, apices obtuse. Cypselas obovoid, slightly compressed, ribbed, transversely and finely rugose, with a swollen lateral attachment scar and an apical rim, glabrous; pappus double, outer of linear-subulate persistent scales, inner usually a ring bearing a single long bristle.