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FNA | Family List | FNA Vol. 7 | Brassicaceae | Draba

83. Draba petrophila Greene, Pittonia. 4: 17. 1899.

Draba helleriana Greene var. blumeri C. L. Hitchcock; D. helleriana var. petrophila (Greene) O. E. Schulz

Perennials; (cespitose, long-lived); caudex simple or branched (covered with persis-tent petioles), not scapose. Stems usually unbranched, rarely branched, 0.3-1.9(-2.8) dm, moderately to densely hirsute throughout, trichomes simple, 0.2-1.3 mm, with short-stalked to subsessile, cruciform, 0.02-0.4 mm, and 2-rayed ones, 0.3-0.9 mm. Basal leaves rosulate; petiolate; petiole ciliate, (trichomes simple, 0.4-1.5 mm); blade oblanceolate, 1-5(-6) cm × 2-5(-10) mm, margins usually entire, rarely denticulate, surfaces pubescent, abaxially with stalked, cruciform trichomes, 0.07-0.5 mm, adaxially often similar, sometimes with fewer, simple and 2-rayed trichomes, 0.4-1.3 mm. Cauline leaves 3-10; sessile; blade ovate to lanceolate or oblong, margins entire or denticulate, surfaces pubescent as basal. Racemes 10-37(-58)-flowered, ebracteate, elongated in fruit; rachis not flexuous, pubescent as stem. Fruiting pedicels divaricate-ascending, straight, 4-10 mm, pubescent throughout, trichomes simple (0.1-0.5 mm) and subsessile, 2-4-rayed, (0.03-0.2 mm). Flowers: sepals oblong, 2-3.5 mm, pubescent, (trichomes simple and 2-rayed); petals yellow, oblanceolate, 3.5-6 × 1.2-1.8 mm; anthers oblong, 0.8-1 mm. Fruits lanceolate to elliptic, often strongly twisted, flattened, 5-11 × 2-3 mm; valves puberulent at least along margin, trichomes simple, antrorse, 0.03-0.15 mm; ovules 14-24 per ovary; style 0.8-1.8(-2.5) mm. Seeds ovoid, 1-1.4 × 0.6-0.9 mm.

Flowering Jul-Sep. Crevices, ledges of cliffs; 1200-2800 m; Ariz.

Draba petrophila is often broadly circumscribed to include the taxon herein called D. viridis. For a discussion of the differences between these species and the closely related D. helleriana, see I. A. Al-Shehbaz and M. D. Windham (2007). Draba petrophila, in the strict sense, is known only from Cochise, Pima, and Santa Cruz counties in southeastern Arizona.


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