Syn. Pl. 2: 397. 1807.
Perennials, to 30+ cm (rhizomatous or stoloniferous). Stems sprawling, ascending, branched mostly from bases. Leaves opposite; sessile; blades spatulate to linear (succulent), margins entire, faces glabrous. Heads radiate [discoid], borne singly. Involucres cylindric to obconic, 4–8+ mm diam. Phyllaries 12–15 in 3+ series (ovate to lanceolate, unequal, succulent to membranous). Receptacles conic, epaleate. Ray florets  3–10, pistillate, fertile; corollas yellow. Disc florets 20–50+, bisexual, fertile; corollas yellow, tubes about equaling narrow, cylindric throats, lobes 5, deltate. Cypselae obconic to clavate or columnar (10-ribbed, glabrous); pappi usually 0, rarely persistent, of 1–5 subulate scales. x = 19.
w North America, nw Mexico, South America.
Species 2 (1 in the flora).