Smithsonian Contr. Knowl. 5(6): 85. 1853.
Annuals, 20–200 cm. Stems erect. Leaves cauline; alternate; petiolate; blades (3-nerved) deltate to ovate, margins entire or toothed, faces usually softly pubescent, sometimes rough-hairy. Heads obscurely radiate or disciform, borne in loose, paniculiform arrays. Involucres hemispheric, 3–5 mm. Phyllaries persistent (outer) or falling, 13, distinct, outer 5 herbaceous (becoming reflexed), inner 6–8 membranous (each becoming cupped around a cypsela). Receptacles convex; paleae of 2 kinds: peripheral purplish-mottled, becoming somewhat fleshy and arcuate-clavate, shed together in pairs with each cypsela; inner 0 or narrowly conic, persistent. Ray-florets 6–8; corollas yellowish (minute), glandular. Disc-florets 10–25+, functionally staminate; corollas yellowish, funnelform, distally glandular and hairy (anthers ± connate). Cypselae (ray) strongly obcompressed to obflattened, obovate, tuberculate, shed with 2 adjacent, ± fleshy paleae; pappi 0 or rudimentary. x = 18.
Ariz., nw Mexico