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

8. Draba arctogena (E. Ekman) E. Ekman, Svensk Bot. Tidskr. 25: 492. 1932.

Draba groenlandica E. Ekman var. arctogena E. Ekman, Svensk Bot. Tidskr. 23: 486. 1930; D. cinerea Adams var. arctogena (E. Ekman) B. Boivin

Perennials; (cespitose); caudex branched (sometimes with persistent leaf remains); sometimes scapose. Stems unbranched, 0.3-1.4 dm, pubescent throughout, trichomes simple, 0.2-1 mm, and 2-6-rayed, 0.05-0.3 mm. Basal leaves rosulate; petiolate; petiole base and margin ciliate, (trichomes mostly simple, 0.2-1 mm); blade oblanceolate to narrowly obovate, 0.4-1.7 cm × 1.5-6 mm, margins entire or with 1-3 teeth on each side, surfaces pubescent with primarily simple trichomes, 0.3-1 mm, abaxially mixed with stalked, 4-10-rayed ones, 0.1-0.2 mm. Cauline leaves 0 or 1; sessile; blade ovate to oblong, margins entire or toothed, surfaces pubescent as basal. Racemes 2-14(-17)-flowered, ebracteate, elongated in fruit; rachis not flexuous, pubescent as stem. Fruiting pedicels suberect to ascending, straight, 1-5(-7) mm, pubescent, trichomes simple and 2-4-rayed. Flowers: sepals ovate, 1.8-2.5 mm, pubescent, (trichomes simple and short-stalked, 2-4-rayed); petals white, spatulate, 3-4 × 1.5-2 mm; anthers ovate, 0.3-0.4 mm. Fruits oblong, plane, flattened, 4-9 × 2-3.5 mm; valves pubescent, trichomes short-stalked, 2-4-rayed, 0.1-0.5 mm, sometimes with simple ones; ovules 20-32 per ovary; style 0.1-0.4 mm (stigma distinctly wider than style). Seeds ovoid, 0.7-1 × 0.5-0.6 mm. 2n = 48.

Flowering Jun-Jul. Scree, sandy hills, gravel flats; 0-450 m; Greenland; N.W.T., Nunavut.

Draba arctogena is sometimes confused with D. norvegica, from which it differs by having less elongated fruiting racemes, abaxial leaf surfaces with 4-10-rayed (versus cruciform or, rarely, 2-6-rayed) trichomes, and fruits with 2-4-rayed trichomes, 0.1-0.5 mm, (versus glabrous or with simple and 2-4-rayed trichomes, 0.05-0.25 mm). The limits of D. arctica , D. arctogena, D. cinerea, and D. oblongata need to be critically evaluated in light of molecular and cytological data.


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