Draba pterosperma

Perennials; (densely cespitose to pulvinate); caudex branched (with persistent leaves, branches sometimes terminating in sterile rosettes); scapose. Stems un-branched, 0.3-1.1 dm, pubescent throughout, trichomes sub-dendritic, 2-7-rayed, (often crisped), 0.2-0.7 mm. Basal leaves (densely imbricate); rosulate; petiolate; petiole base and margin ciliate, (trichomes simple or branched, often crisped, 0.3-1 mm); blade oblanceolate to obovate or spatulate, 0.2-0.7 cm × 1-2.8 mm, margins entire, surfaces densely pubescent (often grayish) with stellate-dendritic, stalked, 5-12-rayed, (often crisped) trichomes, 0.2-0.6 mm. Cauline leaves 0. Racemes 4-12-flowered, ebracteate, elongated in fruit; rachis not flexuous, pubescent as stem. Fruiting pedicels erect (and subappressed to rachis) or ascending, straight, (3-)4-9(-12) mm, pubescent as stem. Flowers: sepals oblong, 3-4 mm, pubescent, (trichomes stalked, branched, crisped); petals yellow, oblanceolate, 6-7 × 1.5-2.5 mm; anthers oblong, 0.7-0.9 mm. Fruits broadly ovate to lanceolate or subelliptic, plane, flattened, 5-10(-13) × (2.5-)3.5-5(-6) mm; valves pubescent, trichomes short stalked, 2-7-rayed, (straight or crisped), 0.15-0.6 mm; ovules 8-12 per ovary; style 1.5-3(-3.8) mm. Seeds (winged), ovate, 1.6-3 × 1.3-1.8 mm; (wing 0.3-0.9 mm wide).

Flowering Jun-Sep. Limestone and marble outcrops, talus, gravel slopes; 1500-2500 m; Calif.

Draba pterosperma is a distinctive species that is restricted to the Marble Mountains of northern California (Siskiyou County).