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

93. Draba ruaxes Payson & H. St. John, Proc. Biol. Soc. Wash. 43: 117. 1930.

Draba ventosa A. Gray var. ruaxes (Payson & H. St. John) C. L. Hitchcock

Perennials; (cespitose, forming tufts); caudex branched (with persistent leaf bases, branches some terminating in sterile rosettes); scapose. Stems un-branched, 0.2-0.6(-0.8) dm, often pubescent throughout, sometimes glabrate distally, trichomes simple, 0.4-1 mm, and 2-4-rayed, 0.1-0.4 mm. Basal leaves rosulate; subsessile; petiole base and margin ciliate, (trichomes simple, 0.4-1.4 mm); blade oblanceolate to obovate or suborbicular, 0.3-1 cm × 2-4.5 mm, margins entire, surfaces pubescent, abaxially with stalked, 2-10-rayed, stellate trichomes, 0.2-0.8 mm, adaxially with simple trichomes, 0.4-1 mm, sometimes with smaller, 2-4-rayed ones, (midvein obscure). Cauline leaves 0. Racemes (2-)4-10(-14)-flowered, ebracteate, elongated in fruit; rachis not flexuous, pubescent as stem or glabrous. Fruiting pedicels ascending to divaricate-ascending, straight or slightly curved upward, 3-7(-9) mm, pubescent or glabrous, trichomes simple and 2-4-rayed. Flowers: sepals ovate, 2-3 mm, pubescent, (trichomes simple with fewer, 2-rayed ones); petals bright yellow, obovate, 4-6 × 2-3.5 mm; anthers oblong, 0.4-0.5 mm. Fruits elliptic to lanceolate or ovate to suborbicular, plane, flattened, 4-8(-10) × 3-4.5 mm; valves puberulent, trichomes simple with fewer 2-rayed ones, 0.1-0.35 mm; ovules 12-16 per ovary; style 0.5-0.9(-1.1) mm. Seeds oblong, 1.5-2 × 1-1.3 mm. 2n = 72.

Flowering Jun-Jul. Rock outcrops, talus slopes, ridges, alpine summits; 500-2400 m; Alta., B.C., Yukon; Alaska, Wash.

C. L. Hitchcock (1941) treated Draba ruaxes as a variety of D. ventosa; as demonstrated by G. A. Mulligan (1971b), the two are quite distinct. Draba ruaxes is an outcrossing hexaploid with well-formed anthers and pollen, and abundant, simple trichomes on leaves, stems, sepals, and fruits. By contrast, D. ventosa is an apomictic triploid with abortive anthers and/or pollen, and no simple trichomes anywhere on the plant.


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