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FNA | Family List | FNA Vol. 4 | Cactaceae | Opuntia

29. Opuntia basilaris Engelmann & J. M. Bigelow, Proc. Amer. Acad. Arts. 3: 298. 1856.

Beavertail pricklypear

Shrubs, forming clumps, 1-2(-3) segments tall, to 7-40 cm. Stem segments not disarticulating, blue- to yellow-green, sometimes tinged maroon-purple, flattened, spat-ulate to broadly obovate or subcircular, thick, 5-22(-35) × 2-13.5(-16) cm, nearly smooth, papillose to puberulent (rarely glabrous); areoles 4-16(-19) per diagonal row across midstem segment, circular to elliptic, 3-5 × 3 mm; wool white to tan, aging gray. Spines 0(-8) per areole, when present, usually in distal areoles, spreading, yellow, straight, acicular, 5-25 mm. Glochids numerous, nearly filling areoles, yellow to red-brown or dark brown, to 3 mm. Flowers: inner tepals pink to magenta throughout (rarely white), 25-40 mm; filaments red-magenta (rarely pale); anthers yellowish; style white to pink; stigma lobes white to cream. Fruits maturing tan, 20-40 × 15-23 mm, dry at maturity, puberulent, spineless (except in var. treleasei); umbilicus 5-12 mm deep; areoles 24-76. Seeds yellowish to tan, ± subspheric but angular, thick, 6.5-9 × 6.5-7 mm, sides smooth or bearing 1-3 depressions; girdle protruding to 1 mm.

Varieties 4 (4 in the flora): sw United States, n Mexico.

1 Stem segments bearing spines in at least several of distal areoles   29b var. treleasei
+ Stem segments essentially spineless (rarely 1-few per stem segment)   (2)
2 (1) Stem segments broadly obovoid to subcircular, erect; areoles (8-)10-16(-19) per diagonal row across midstem segment..   29a var. basilaris
+ Stem segments spatulate to elongate, oblong, usually decumbent; areoles 4-8(-9) per diagonal row across midstem segment   (3)
3 (2) Stem segments spatulate, apex rounded; areoles 4-8(-9) per diagonal row across midstem segment; Arizona, Utah.   29c var. longiareolata
+ Stem segments oblong to narrowly spatulate to subcylindric, apex truncate to rounded; areoles 4-6(-7) per diagonal row across midstem segment; California   29d var. brachyclad


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