Erect annual or sometimes apparently perennial herbs 5-100 cm tall; stem terete or weakly angled, usually purplish, glabrous or minutely puberulent, usually much branched above. Leaves linear to narrowly oblanceolate, obtuse to acute, mucronate or aristate, basally ciliate with several pairs of bristles, glabrous to scaberulous on one or both surfaces, punctate on the undersurface with scattered small round oil glands. Inflorescence of few-to many-flowered cymose clusters or solitary heads; peduncles short to elongate, bracteolate. Heads small, radiate; involucres cylindric to narrowly campanulate, the bracts 5, little if at all imbricate, linear-oblanceolate, acute to acuminate, narrowly indurate-keeled, basally gibbous, glabrous, variously punctate; ray florets 5, the corollas 3-7 mm long, yellow or becoming reddish, glabrous, the tubes slender, the ligules usually involute; disc florets 5-9, the corollas 2-4 mm long, bilabiate. Achenes 2-3 mm long, black, short-strigillose; carpopodium short, knoblike; pappus of 2-20 scabrid bristles 2.5-4 mm long.
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