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

9. Draba argyrea Rydberg, Bull. Torrey Bot. Club. 30: 251. 1903.

Draba argyrea var. glabrescens O. E. Schulz

Perennials; caudex branched (branches loose, creeping, sometimes terminating in sterile shoots); scapose. Stems unbranched, (0.2-)0.3-0.8 (-1.1) dm, pubescent prox-imally, glabrous distally, trichomes short-stalked to subsessile, 5-8-rayed, 0.05-0.2 mm. Basal leaves rosulate; subsessile; petiole base and margin not ciliate, (midvein obscure abaxially); blade oblanceolate to obovate, 0.3-0.7(-1.2) cm × 1-2.5(-4) mm, margins entire, surfaces canescent with short-stalked, 8-12-rayed, stellate trichomes, 0.1-0.2 mm. Cauline leaves 0. Racemes 2-8(-12)-flowered, ebracteate, elongated in fruit; rachis slightly flexuous, usually glabrous, rarely sparsely pubescent as stem. Fruiting pedicels divaricate-ascending, straight or slightly curved upward, (4-)5-12(-19) mm, glabrous. Flowers: sepals ovate, 2-3 mm, pubescent, (trichomes 4-6-rayed); petals yellow, oblanceolate, 4-6 × 1.5-3 mm; anthers ovate, 0.5-0.6 mm. Fruits lanceolate to elliptic or ovate, plane or slightly twisted, flattened, 5-11 × 2-3.5(-4.5) mm, (symmetric); valves often puberulent, sometimes glabrous, trichomes simple and subsessile, 2-4-rayed, 0.03-0.2 mm; ovules 8-14 per ovary; style (0.7-)1-1.8(-2.4) mm. Seeds oblong, 1.2-1.8 × 0.8-1.1 mm. 2n = 36.

Flowering Apr-Jul. Rock crevices, ledges, talus slopes; 1000-3100 m; Idaho.

M. A. Beilstein and M. D. Windham (2003) hypothesized that Draba argyrea is an allopolyploid derived through hybridization between D. lonchocarpa and D. sphaerocarpa. The species is restricted to Blaine, Boise, Custer, and Elmore counties in central Idaho.


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