Helminthotheca

Annual, biennial or perennial taprooted herbs, with stiff tubercle-based hairs, often spinose or finer with 3–5-fid hooked apices; stems usually branched. Leaves basal and cauline, alternate, flat, margins sinuate to pinnatisect. Capitula pedunculate, in loose terminal corymbs or umbel-like clusters, often forming a panicle; involucre cylindric, bracts imbricate, 2-seriate, unequal, spinose, outer ones ovate, herbaceous, inner ones longer, long-acuminate, with scarious margins; receptacle flat, naked, pitted. Florets ligulate, bisexual, yellow; ligule linear, 5-toothed; anthers sagittate at base, with minute triangular appendages at apex; style bilobed, with long, narrow-linear, minutely hairy branches. Cypselas obovoid-fusiform, usually ribbed, transversely wrinkled, glabrous, with a long fragile filiform beak, sometimes absent in outer cypselas; pappus 1-seriate, of plumose bristles joined at base, sometimes plumose or reduced to scales in outer cypselas.