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

115. Draba trichocarpa Rollins, Contr. Gray Herb. 214: 4. 1984.

Perennials; (cespitose, densely pulvinate); caudex branched (covered with persistent leaves, branches sometimes terminating in sterile rosettes); scapose. Stems unbranched, 0.07-0.35 dm, pubescent throughout, trichomes (soft), stalked, subdendritic, (somewhat crisped), 0.1-0.5 mm, (simple ones absent). Basal leaves (densely imbricate); rosulate; sessile; blade oblong to obovate, 0.2-0.4 cm × 0.5-1.5 mm, margins entire, (ciliate, trichomes simple and branched, subdendritic, or spurred, 0.3-0.8 mm), surfaces sparsely pubescent, abaxially with stalked, 4-6-rayed stellate trichomes, 0.1-0.4 mm, adaxially with simple and 4-6-rayed trichomes, mainly on distal 1/2. Cauline leaves 0 (or 1); sessile; blade similar to basal. Racemes 2-9-flowered, ebracteate, slightly elongated in fruit; rachis not flexuous, pubescent as stem. Fruiting pedicels divaricate-ascending to ascending, straight, 1-4.5 mm, pubescent as stem. Flowers: sepals ovate, 2-3 mm, pubescent, (trichomes short-stalked); petal color unknown, broadly obovate, 2-4 × 2-2.5 mm; anthers oblong, 0.5-0.6 mm. Fruits ovoid, plane, slightly inflated basally, flattened distally, 2-6 × 2-3.5 mm; valves densely pubescent, trichomes 4-rayed, 0.1-0.4 mm, (often some rays spurred or branched); ovules 4-10 per ovary; style 0.3-0.7 mm. Seeds oblong, 1.4-2 × 0.8-1.2 mm.

Flowering Jun-Jul. Gravelly metamorphic soil at ecotone between sagebrush steppe and open conifer forests; of conservation concern; ca. 2000 m; Idaho.

Draba trichocarpa is an apomictic polyploid that appears to be closely related to D. novolympica. It is readily distinguished from that species by the primarily dendritic trichomes (and absence of simple trichomes) on the stems, pedicels, and fruits. Draba trichocarpa is known from the Stanley Basin of central Idaho (Custer County).


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