Draba macounii

Perennials; (cespitose); caudex simple or branched (with persistent leaf bases, branches sometimes terminating in sterile rosettes); scapose. Stems unbranched, (0.06-)0.1-0.4 (-0.6) dm, usually pubescent, rarely glabrous, trichomes simple and stalked, 2-4-rayed, 0.15-0.9 mm. Basal leaves rosulate; petiole (obscure), margin ciliate, (trichomes simple, 0.3-1 mm); blade oblanceolate to obovate, (0.4-)0.6-1(-1.5) cm × (1-) 2-4 mm, margins entire, surfaces usually pubescent abaxially, rarely glabrous, with short-stalked, 2-5-rayed trichomes, 0.1-0.5 mm, adaxially glabrous or pubescent with simple and short-stalked, 2-rayed trichomes. Cauline leaves 0. Racemes 3-10(-13)-flowered, ebracteate, (subumbellate), slightly elongated in fruit; rachis not flexuous, usually pubescent as stem, rarely glabrous. Fruiting pedicels horizontal to divaricate (not expanded basally), curved upward, 1.5-4.5(-6) mm, abaxially pubescent as stem, adaxially usually glabrous, rarely throughout. Flowers: sepals ovate, 1.5-2.5 mm, glabrous or pubescent, (trichomes simple and short-stalked, 2- or 3-rayed); petals pale yellow, spatulate, 2.7-4 × 1-2 mm; anthers ovate, 0.2-0.3 mm. Fruits subglobose to ovoid or ellipsoid, plane, inflated at least basally, 4-8 × 2-4.5 mm; valves glabrous; ovules 10-14(-16) per ovary; style 0.1-0.5 mm. Seeds ovoid, 1-1.2 × 0.6-0.8 mm. 2n = 64.

Flowering Jun-Aug. Rock outcrops, talus, tundra; 700-2800 m; Alta., B.C., Yukon; Alaska, Mont.

Draba macounii is often confused with the circumpolar decaploid (2n = 80) D. alpina. Plants of the former have scapes (0.6-)1-4(-6) cm, fruiting pedicels divaricate to horizontal, gently curved, and 1.5-4.5(-6) mm, and petals pale yellow, spatulate, and 2.7-4 × 1-2 mm. By contrast, D. alpina has scapes (3-)5-17(-28) cm, fruiting pedicels divaricate-ascending to ascending, often straight, and (3-)4-14(-30) mm, and petals bright yellow, obovate, and 3.5-5 × 1.7-2.5 mm. R. C. Rollins (1993) indicated that the species occurs in Colorado, but we have not seen any material from that state.