173. Acamptopappus (A. Gray) A. Gray, Proc. Amer. Acad. Arts. 8: 634. 1873.
Goldenhead [Greek akamptos, stiff or unbending, and pappus, alluding to thick pappus elements]
Guy L. Nesom
Haplopappus Cassini sect. Acamptopappus A. Gray, Mem. Amer. Acad. Arts, n. s. 4: 76. 1849 (as Aplopappus)
Shrubs, 20–40 cm (deciduous; taproots woody). Stems erect (older portions gray, usually with shredding bark), branched, spinescent with age, glabrous or hirtellous. Leaves cauline; alternate (sometimes in axillary fascicles); petiolate or sessile; blades (gray-green) 1-nerved, narrowly lanceolate or narrowly obovate or spatulate, margins entire, faces glabrous, scabrous, or scabro-hirtellous, eglandular. Heads radiate or discoid, borne singly or in loose corymbiform arrays (pedunculate). Involucres campanulate to hemispheric or globose, (4–13 ×) 7–16 mm. Phyllaries 13–25 in 3 series, appressed (reflexing at maturity, bases yellowish, apices green), 1-nerved (flat), broadly ovate to elliptic-ovate, unequal, margins broadly hyaline, lacerate, faces glabrous. Receptacles flat to slightly convex, deeply pitted (pit margins ± lacerate), epaleate. Ray florets usually 5–14, sometimes 0, pistillate, fertile; corollas yellow. Disc florets 13–45, bisexual, fertile; corollas yellow, tubes longer than funnelform throats, lobes 5, reflexed, lanceolate; style-branch appendages triangular-lanceolate. Cypselae obconic, compressed, nervation not evident, faces densely sericeous to villous (some hairs ascending-spreading, others appressed and tortuous); pappi persistent, of 18–22, variably thick, broadly flattened, subequal, marginally barbellate or barbellulate to smooth, apically attenuate (ray) to spatulate (disc), setiform scales (heights equaling disc corollas) in 1–2 series, plus much shorter bristles or setae. x = 9.
Species 2 (2 in the flora): sw United States.
Acamptopappus is essentially endemic to the Mojave Desert of California, Arizona, Nevada, and Utah. The genus is recognized as low, white-barked, desert shrubs with pedunculate heads, borne singly or in loose, corymbiform arrays, with ovate phyllaries with broad hyaline margins, 0 or 5–14 yellow rays, sericeous to villous cypselae, and thick pappus scales.
Lane, M. A. 1988. Generic relationships and taxonomy of Acamptopappus (Compositae: Astereae). Madroño 35: 247–265.