in A. von Humboldt and A. J. Bonpland, Pl. Aequinoct. 1: 143, plate 41. 1807.
Perennials or subshrubs, (10–)30–100 cm. Stems mostly erect, branched. Leaves cauline; opposite; ± petiolate; blades deltate or rounded-deltate to ovate [lanceolate to linear], margins usually dentate, faces glabrous or glabrate. Heads radiate, in corymbiform arrays [borne singly]. Involucres narrowly cylindric [campanulate], 2–3[–6] mm diam. Phyllaries persistent, 3–5 in 1 series (distinct, oblong or lanceolate to linear, herbaceous, conduplicate, streaked with 8–12+ translucent nerves, margins often membranous). Receptacles convex, paleate (paleae similar to phyllaries, membranous, each enfolding a floret). Ray florets 1–5, pistillate, fertile; corollas whitish (tubes often longer than laminae). Disc florets 3–20+, functionally staminate; corollas whitish, tubes longer than abruptly ampliate, campanulate to funnelform throats, lobes 5, lanceolate to lance-linear (filaments hairy; anthers green). Cypselae ± ellipsoid [fusiform to clavate], ± obcompressed, smooth or fine-ribbed, glabrous (bases carunculate); pappi 0 [5–6, erose scales]. x = 12.
sw United States, Mexico.
Species ca. 10 (1 in the flora).