Draba streptobrachia

Perennials; caudex branched (often with persistent leaf remains, branches not creeping); not scapose. Stems unbranched, (0.1-)0.2-1(-1.3) dm, pubescent throughout, trichomes subsessile (often crisped), 3-5-rayed, stellate, 0.03-0.25(-0.4) mm, (rays sometimes forked). Basal leaves rosulate; petiole (obscure), usually not ciliate, rarely sparsely pubescent, (trichomes simple, to 0.6 mm); blade oblanceolate to linear-oblanceolate, (0.4-)0.5-3(-4) cm × 1-5 mm, margins entire, surfaces pubescent with short-stalked (crisped), 3-8-rayed trichomes, 0.05-0.4 mm. Cauline leaves (1 or) 2-4 (or 5); sessile; blade oblong to ovate or linear, margins entire, surfaces pubescent as basal. Racemes 4-10 (-18)-flowered, ebracteate, elongated in fruit; rachis not flexuous, pubescent as stem. Fruiting pedicels ascending, usually straight, rarely curved upward, (2-)3-8(-12) mm, pubescent as stem. Flowers: sepals ovate, 2-3 mm, pubescent, (trichomes simple and short-stalked, 2-4-rayed); petals yellow, spatulate, 3-5 × 1.5-3 mm, (clawed); anthers ovate, 0.25-0.4 mm. Fruits (not appressed to rachis), ovate to elliptic or lanceolate, slightly twisted or plane, flattened, (3-)5-10 × 2-4 mm; valves often pubescent, occasionally glabrous, trichomes simple and minutely stalked, 2-4-rayed, 0.03-0.25 mm; ovules 10-16(-18) per ovary; style 0.3-0.8(-1.2) mm. Seeds oblong, 1-1.6 × 0.6-1 mm. 2n = ca. 64.

Flowering Jul-Aug. Alpine tundra, scree, ridges and alpine slopes, turf, fellfields, talus slopes, crevices in rock ledges, loose soils; 3200-4000 m; Colo.

As indicated by Price, Draba streptobrachia is an apomict, yielding abundant, well-developed seed despite producing only abortive pollen. Morphological studies (M. D. Windham, unpubl.) suggest that the species may be an allopolyploid containing a genome from D. crassa.