10. Opuntia strigil Engelmann, Proc. Amer. Acad. Arts. 3: 290. 1856.
Shrubs, erect to sprawling, to 1 m. Stem segments not easily detached, green, flattened, obovate to circular, 10-17 × 8.5-14.5 cm, nearly smooth, glabrous; areoles 7-10 per diagonal row across midstem segment, oblong to elliptic, 3-5 × 2.5-3.5 mm; wool yellow-brown to brown, aging gray. Spines 5-8(-10) per areole, best developed in distal areoles, usually reflexed, spreading or some erect in marginal areoles, red-brown (often with darker annular rings) with yellow tips, aging blackish, straight or weakly curved, not or slightly flattened near bases; central spines 1(-2), much longer and stouter, ± acicular, 10-40 mm. Glochids crowded in crescent at adaxial edge of areole and subapical tuft, radiating and well developed in old stem segments, yellow, to 3 mm. Flowers: inner tepals cream to lemon yellow, orangish abaxially on midvein areas, broadly spatulate-apiculate, 20-30 mm; filaments cream-yellow; anthers pale yellow; style pale cream; stigma lobes pale greenish yellow. Fruits red, subspheric, 15-28 × 12-23 mm, fleshy, glabrous, spineless; umbilicus 4-5 mm deep; areoles 24-36. Seeds tan, subcircular to reniform, flattened, warped, 3-4 × 2.7-3.5 mm, 2 mm thick; girdle protruding 0.5-0.8 mm. 2n = 22, 44.
Flowering spring (Apr-May). Desert scrub, limestone hills and plains; 900-1400 m; Tex.
Opuntia strigil is reminiscent of a brown-spined form of O. chlorotica.