Annuals [perennials or subshrubs], 60–200 cm. Stems sprawling to erect, branched from bases or ± throughout. Leaves mostly cauline; opposite (proximal) or alternate; petiolate [sessile]; blades 3-nerved, ovate to rhombic or lanceolate, bases cuneate to rounded, margins coarsely toothed, faces glabrous or ± scabrous. Heads radiate, borne singly. Involucres rotate to hemispheric, 12–20 mm diam. Phyllaries persistent, 5–8[–21] in 1(–2) series (green, oblong to linear). Receptacles low-conic, paleate (paleae each closely investing subtended floret, each forming a hard perigynium around a fruit and shed with it). Ray florets 5–8, neuter; corollas (readily falling) yellow to orange. Disc florets 10–50, bisexual, fertile; corollas usually yellow to orange, sometimes with purple, tubes much shorter than cylindric throats, lobes 5, lance-linear. Cypselae (within perigynia) weakly compressed, obliquely obovoid or arcuate (glabrous); pappi 0, or coroniform (of distinct or connate scales or bristles). x = 12.

Distribution

s United States, Mexico, Central America, one species in Old World tropics.

Discussion

Species ca. 12 (1 in the flora).

Selected References

Feddema, C. 1966. Systematic Studies in the Genus Sclerocarpus and the Genus Aldama (Compositae). Ph.D. dissertation. University of Michigan.

Lower Taxa

Sclerocarpus uniserialis