J. Bot. (Hooker) 3: 321. 1841.
Annuals, to 40 cm (sweet scented). Stems erect, branched. Leaves cauline; opposite (proximal) or alternate (mostly); sessile; blades mostly linear, sometimes pinnately lobed, ultimate margins entire, faces glabrous (often granular-glandular). Heads discoid or disciform, in corymbiform or paniculiform arrays. Involucres ovoid to campanulate, 3–4+ mm diam. Phyllaries persistent, 3–6+ in 1–2 series (± erect in fruit, distinct, obovate, herbaceous to membranous or scarious, flat or weakly cupped at bases, glabrous or granular-glandular). Receptacles conic, pitted or smooth, glabrous, epaleate. Ray florets 0 (or inconspicuous; peripheral 3–8 florets pistillate, fertile; corollas yellow, tubular or nearly so). Disc florets 2–25+, bisexual, fertile; corollas yellow, tubes about equaling campanulate throats, lobes 5, ± deltate. Cypselae mostly obpyramidal, (3–)4-angled, hairy; pappi persistent, of 7–10+ oblong to spatulate scales. x = 8.
Calif., nw Mexico, South America.