Index Seminum (St. Petersburg) 2: 42. 1836.
Plants 1–50 cm. Heads depressed-spheric, 2–4 × 3–6 mm. Receptacles depressed-spheric, mostly 0.3–0.6 mm, heights 0.5–0.8 times diams. Pistillate paleae 4–7(–8) in 1 series, longest 2–4 mm; wings obscure, withering, lateral, ± erect, narrowly oblanceolate, involute; bodies galeate, cartilaginous to bony throughout, sericeous to lanuginose. Staminate paleae 0. Staminate corollas 1–2 mm, lobes usually 5. Cypselae 1.4–2.6 mm, corolla scars ± median; pappi: staminate 0 or of 1, ± smooth bristle 0.9–1.5 mm.
Calif., Oreg., nw Mexico.
Varieties 2 (2 in the flora).
Though common and often found on recent disturbances within its range, Micropus californicus does not appear to be particularly invasive or weedy. The mature pistillate paleae, with roughly the profile of a harp or of an inverted lower-case letter “q,” are distinctive. That shape and the accompanying dense, cottony indument of the common variety explain the vernacular names. By contrast, pistillate paleae of M. amphibolus have roughly the profile of a human head wearing a billed cap.
Within the more limited range of var. subvestitus, the two varieties are broadly sympatric, usually in separate populations, occasionally in mixed populations that sometimes include intermediate plants.