82. Draba pennellii Rollins, J. Arnold Arbor. 64: 502. 1983.
Perennials; (cespitose, often forming mats); caudex branched (elongated, with persistent leaf bases, branches sometimes terminating in sterile rosettes); sometimes scapose. Stems unbranched, (0.15-)0.3-0.7(-1) dm, pubescent proximally, trichomes simple and spurred, 0.4-0.8 mm, and short-stalked, 2-4-rayed, 0.1-0.4 mm, (sometimes with simple trichomes distally). Basal leaves subrosulate; sessile; blade oblanceolate to oblong, (0.3-)0.5-0.8 cm × 1-3 mm, (base ciliate, trichomes simple, 0.2-0.8 mm), margins entire, (not ciliate), surfaces usually pubescent, with stalked, (2-)4 (or 5)- rayed trichomes, 0.2-0.5 mm, adaxially sometimes glabrate, or primarily with simple trichomes, 0.3-0.8 mm. Cauline leaves (0 or) 1-4; sessile; blade ovate to oblong, margins entire, surfaces pubescent as basal. Racemes (3-)7-15(-20)-flowered, ebracteate, elongated in fruit; rachis not flexuous, pubescent as stem. Fruiting pedicels divaricate-ascending to ascending, straight, 3-10 mm, pubescent, trichomes simple and short-stalked, 2-4-rayed, (0.1-0.4 mm). Flowers: sepals ovate to oblong, 2-3 mm, pubescent, (trichomes simple, with fewer, short-stalked, 2-rayed ones); petals white, obovate, 3.5-6 × 1.5-2.8 mm; anthers oblong, 0.5-0.6 mm. Fruits broadly or, rarely, narrowly lanceolate to elliptic or ovate, plane or slightly twisted, flattened, (4)5-8(-10) × 2-3.2 mm; valves (each with distinct midvein), pubescent, trichomes simple and short-stalked, 2-rayed, 0.08-0.2 mm; ovules 12-24 per ovary; style (0.7-)1-1.8(-2.1) mm. Seeds oblong, 0.9-1.3 × 0.7-1 mm. 2n = 32.
Flowering May-Jul. Rock outcrops and talus slopes in pinyon-juniper, sagebrush, mountain shrub, and mixed conifer communities; of conservation concern; 1900-3500 m; Nev.
Draba pennellii is known from White Pine County in east-central Nevada. It is easily distinguished from other white-flowered species in the region by its elongated, many-branched caudices, long styles, usually few-leaved or, rarely, leafless flowering stems, and distinct midvein on fruit valves.