7. Grusonia parishii (Orcutt) Pinkava, J. Arizona-Nevada Acad. Sci. 32: 50. 1999.
Opuntia parishii Orcutt, W. Amer. Sci. 10: 81. 1896; Corynopuntia parishii (Orcutt) F. M. Knuth; C. stanlyi (Engelmann ex B. D. Jackson) F. M. Knuth var. parishii (Orcutt) Backeberg; O. stanlyi Engelmann ex B. D. Jackson var. parishii (Orcutt) L. D. Benson
Shrubs, forming mats, 10-20 cm in series of usually 1-2 stem segments. Roots diffuse. Stem segments clavate, 5-9 × 2-3 cm; tubercles prominent, 15-25 mm, narrow, 4-6 times longer than wide, obscured by interlacing spines; areoles 5 mm in diam.; wool grayish white. Spines 14-17(-22) per areole, mostly in distal areoles or ± uniformly distributed, white to brownish, tipped yellow; major 5-6 abaxial spines strongly deflexed, flattened, longest white margined, 25-45(-58) mm; central spine brown or white, long tapered; major ca. 5 adaxial spines divergent, blackish or brown to tan, subterete, angular-flattened at base, longest to 42 mm. Glochids adaxial in areoles, yellow, 5-8 mm. Flowers: inner tepals pale yellow with narrow reddish midstripes, 15-22 mm; filaments pinkish or greenish to pale yellow; style whitish to pale yellow or dull pinkish; stigma lobes white, greenish white or pale yellow. Fruits yellow, 35-55 × 15-20 mm, fleshy, spineless, densely yellow glochidiate; areoles 35-52. Seeds yellowish white, 4-4.5 × 3.5-4.5 mm, smooth. 2n = 22.
Flowering late spring-early summer (May-Jul). Mojave and Sonoran deserts, silty, sandy, or gravelly flats, dunelets, hills; 300-900 m; Ariz., Calif., Nev.
L. D. Benson (1969) segregated plants of the southern Arizona populations, which are less robust than the others, as "Opuntia stanlyi var. peeblesiana;" unfortunately he included with its type other specimens that belong to Grusonia kunzei. Diploid plants of G. parishii have spineless (but glochidate) fruits; tetraploid plants of G. kunzei have spiny and glochidate fruits.