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

90. Draba ramulosa Rollins, Contr. Gray Herb. 214: 6. 1984.

Perennials; (loosely matted, grayish); caudex branched (with persistent leaf bases, branches creeping, sometimes terminating in sterile rosettes); not scapose. Stems unbranched, 0.4-0.6 dm, densely pubescent throughout, trichomes dendritic, 3-6-rayed, (often crisped), 0.1-0.4 mm. Basal leaves (imbricate); not rosulate; sessile; blade obovate to oblanceolate, 0.4-1.1 cm × 2-3.2 mm, margins entire, (base and margins not ciliate), surfaces pubescent with stalked, 4-8-rayed trichomes, 0.1-0.5 mm, (sometimes 1 or more rays spurred), adaxially sometimes trichomes simple. Cauline leaves 2 or 3 (sometimes basal leaves spaced, flowering stem appearing to 8-leaved); sessile; blade oblong to ovate, margins entire, surfaces pubescent as basal. Racemes 4-15-flowered, ebracteate or proximalmost 1 or 2 flowers bracteate, slightly elongated in fruit; rachis not flexuous, pubescent as stem. Fruiting pedicels divaricate-ascending, usually straight, rarely curved upward, 3-6 (-10) mm, pubescent, trichomes 3-6-rayed, (crisped, 0.1-0.4 mm), and, sometimes, simple. Flowers: sepals broadly ovate, 1.7-2.4 mm, pubescent, (trichomes short-stalked, 2-5-rayed); petals yellow, obovate to oblanceolate, 3-4.5 × 1.5-2.5 mm; anthers ovate, 0.4-0.5 mm. Fruits (not appressed to rachis), ovate to elliptic, plane, flattened, 4-6.5 × 2.5-4 mm; valves densely pubescent, trichomes simple and short-stalked, 2-5-rayed, 0.08-0.35 mm; ovules 6-12 per ovary; style (0.1-)0.3-0.7 mm. Seeds oblong, 1.4-1.8 × 0.8- 1.2 mm.

Flowering Jun-Aug. Rock outcrops, talus, gravelly soils; of conservation concern; 3300-3600 m; Utah.

Molecular and chromosomal data (M. D. Windham, unpubl.) strongly suggest that Draba ramulosa is an allopolyploid species. It is thought to have originated through hybridization between D. sobolifera and a member of the white-flowered, euploid lineage of M. A. Beilstein and M. D. Windham (2003). It is easily distinguished from D. sobolifera by having pale yellow to whitish (versus bright yellow) petals, grayish (versus green) foliage, non-ciliate (versus ciliate) basal leaves pubescent with 4-8-rayed (versus 2-4-rayed) trichomes, often proximally bracteate (versus ebracteate) racemes, and flattened (versus inflated basally) fruits. Draba ramulosa is known from the Tushar Mountains in south-central Utah (Beaver and Piute counties).


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