17. Malacothrix stebbinsii W. S. Davis & P. H. Raven, Madroño. 16: 265, fig. 2e. 1962.
Malacothrix clevelandii A. Gray var. stebbinsii (W. S. Davis & P. H. Raven) Cronquist
Annuals, 5–60 cm. Stems 1–5+, ± erect, branched distally, sparsely leafy, glabrous. Cauline leaves: proximal obovate, pinnately lobed (lobes 3–5+ pairs, triangular to oblong or linear), not fleshy, ultimate margins entire or dentate, faces glabrous; distal reduced (usually with 2 lobes near bases). Calyculi of 5–8+, ovate to lanceolate bractlets, hyaline margins 0.05–0.2 mm. Involucres ± campanulate, 7–10 × 3–6 mm. Phyllaries 16–20+ in 2–3 series, lanceolate to lance-linear, hyaline margins 0.05–0.1 mm wide, faces glabrous. Receptacles not bristly. Florets 19–70; corollas usually yellow, sometimes white, 6–7 mm; outer ligules exserted 1–2 mm. Cypselae ± cylindro-fusiform, 1.7–2.3 mm, ribs extending to ca. 0.1–0.2 mm short of apices (minutely hirtellous or muriculate), ± equal (distal 0.1–0.2 mm of cypselae smooth); pappi persistent, of 8–15+, needlelike teeth plus 1(–2) bristles. Pollen 70–100% 4-porate. 2n = 28.
Flowering Mar–Jun. Gravelly soils beneath shrubs, along ditches, near streams, in sagebrush steppes, creosote bush scrublands; 300–1300 m; Ariz., Calif., Nev., N.Mex.; Mexico (Sonora).
Malacothrix stebbinsii grows in the Mojave Desert (Borrego area, California) and the Sonoran Desert (Santa Catalina, Mazatzal, Baboquivari, and Santa Rita mountains, and elsewhere in Arizona).