Silybum

Robust annual or biennial herbs, spiny; stems erect, much-branched below, ribbed, terete. Leaves basal and cauline, alternate, margins thickened, toothed to pinnatisect, spiny, variegated with white veins. Capitula ovoid, terminal, solitary; involucral bracts in many series, leathery, unequal, glabrous, with a spinose or acuminate apical appendage; receptacle flat, densely hairy. Florets bisexual, fertile, tubular, more or less equal, pink or purple; corolla deeply 5-lobed, glabrous; anthers sagittate at base, with acute appendages at apex; style bilobed, with appressed linear terete branches, apices diverging. Cypselas ovoid to obovoid, somewhat compressed, glabrous; pappus of several series of barbellate bristles united in a ring at base, deciduous as a single unit.