Draba exunguiculata

Perennials; (densely cespitose); caudex branched (covered with persistent, somewhat thickened, dry petioles); not scapose. Stems unbranched, 0.15-0.7 dm, glabrous throughout or sparsely pubescent, trichomes simple, 0.3-0.9 mm. Basal leaves rosulate; petiolate; petiole ciliate, (trichomes simple, 0.3-1.1 mm); blade linear to linear-oblanceolate, (0.5-)0.8-2(-2.5) cm × 1-3 mm, margins entire, (pubescent as petiole), surfaces abaxially sparsely pubescent with simple and stalked, 2- or 3-rayed trichomes, 0.1-0.4 mm, adaxially glabrous or subapically sparsely pubescent with simple trichomes. Cauline leaves 1-4; sessile; blade linear to linear-oblanceolate, margins entire, surfaces pubescent as basal. Racemes 4-13(-20)-flowered, ebracteate, elongated in fruit; rachis not flexuous, usually glabrous, rarely sparsely pubescent, trichomes simple, to 1 mm. Fruiting pedicels divaricate-ascending, straight or slightly curved upward, 1-6 mm, usually glabrous, rarely with few, simple trichomes. Flowers: sepals ovate, 2-2.5 mm, pubescent, (trichomes simple); petals (erect), yellow, obovate, 2-2.5(-3) × 1.5-2 mm, (not clawed); anthers oblong, 0.6-0.9 mm. Fruits lanceolate to oblong-lanceolate, plane, flattened, 5-13 × 1.5-3 mm; valves glabrous; ovules 20-24 per ovary; style 0.3-1 mm. Seeds ovoid, 1-1.3 × 0.6-0.8 mm. 2n = 56 ± 5.

Flowering Jul-Aug. Open knolls, talus, gravelly alpine slopes, rocky alpine tundra; of conservation concern; 3600-4300 m; Colo.

Draba exunguiculata occupies alpine areas of Clear Creek, El Paso, Grand, and Summit counties in central Colorado. Draba grayana is found in the same general area; both species are apomicts that occasionally grow sympatrically. Draba exunguiculata is easily distin-guished from D. grayana by having stems and fruiting pedicels glabrous or sparsely pubescent with simple trichomes (versus moderately to densely pubescent with simple and 2- or 3-rayed trichomes), and by having erect, non-clawed petals, 2-3 mm and slightly longer than sepals (versus flared, clawed petals 3-4.5 mm and nearly twice as long as sepals).