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

86. Draba porsildii G. A. Mulligan, Canad. J. Bot. 52: 1795, fig. 8. 1974.

Draba nivalis Liljeblad var. brevicula Rollins; D. porsildii var. brevicula (Rollins) Rollins

Perennials; (cespitose); caudex branched (with persistent leaf remains); often scapose. Stems unbranched, 0.2-1.2 dm, sparsely pubescent proximally, trichomes short-stalked, 3-5- rayed, (non-crisped), 0.2-0.4 mm, glabrous distally. Basal leaves rosulate; subsessile or shortly petiolate; petiole base and margin ciliate proximally, (trichomes simple, subsetiform, stiff, 0.3-0.9 mm); blade oblanceolate to obovate, 0.4-1.5 cm × 1-3 mm, margins entire, surfaces pubescent, abaxially with stalked, 6-12-rayed, (non-crisped) trichomes, 0.2-0.5 mm, (midvein obscure), adaxially similar, or with simple trichomes on proximal 1/2. Cauline leaves 0 or 1; sessile; blade oblong to lanceolate, margins entire, surfaces pubescent as basal. Racemes 3-13-flowered, ebracteate, elongated in fruit; rachis not flexuous, glabrous. Fruiting pedicels divaricate-ascending, straight, 1-4(-8) mm, glabrous. Flowers: sepals ovate, 1.5-2 mm, pubescent, (trichomes simple and 2-rayed); petals white, spatulate, 2-4 × 1-1.7 mm; anthers ovate, ca. 0.2 mm. Fruits ovate to oblong, plane, flattened, 4-7.5 × 1.7-3 mm; valves glabrous; ovules 12-16 per ovary; style 0.1-0.3(-0.5) mm. Seeds ovoid, 0.7-1 × 0.5-0.6 mm. 2n = 32.

Flowering Jun-Jul. Rock outcrops, talus, meadows, gravel slopes; 600-3000 m; Alta., Yukon; Alaska, Mont., Wyo.

According to H. H. Grundt et al. (2004), tetraploid Draba porsildii probably originated from a diploid ancestor such as D. lonchocarpa. The Wyoming plants are a close match to the type of the species, though they have distinctly shorter pedicels. Some of the Alaskan plants are more problematic; they have finer and more branched trichomes, larger flowers, longer pedicels, and longer styles than the type. It is likely that they belong to another species; detailed molecular and cytological studies on this complex are needed before any meaningful conclusions are reached.


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