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

15. Draba bifurcata (C. L. Hitchcock) Al-Shehbaz & Windham, Harvard Pap. Bot. 12: 411. 2007.

Draba helleriana Greene var. bifurcata C. L. Hitchcock, Revis. Drabas W. N. Amer., 39, plate 3, fig. 21e. 1941

Biennials or, rarely, perennials; caudex simple or branched; not scapose. Stems branched or unbranched, 1-3.9 dm, pubescent throughout or proximally, trichomes simple, 0.3-1.4 mm, often with smaller, 2 (or 3)-rayed ones. Basal leaves (soon withered); rosulate; petiolate; petiole ciliate, (trichomes simple, 0.4-1.1 mm); blade oblanceolate to spatulate, 1-7 cm × 2-12(-26) mm, margins entire or dentate (pubescent as petiole), surfaces pubescent, abaxially with simple trichomes, 0.6-1.1 mm, and stalked, 2- (or 3-)rayed ones, often smaller, adaxially with subsetiform, simple trichomes, 0.5-1.2 mm (rarely with fewer, stalked, 2-rayed ones). Cauline leaves (2-)6-15; sessile; blade lanceolate to ovate or oblong, margins dentate, surfaces pubescent as basal. Racemes 10-51-flowered, ebracteate, elongated in fruit; rachis glabrous or pubescent as stem, not flexuous. Fruiting pedicels horizontal to divaricate, straight, 4-15 mm, glabrous or pubescent, trichomes simple and 2-rayed. Flowers: sepals ovate, 2.5-3.2 mm, pubescent, (trichomes simple and short-stalked, 2-rayed); petals yellow, oblanceolate, 4.5-6.5 × 1.5-2 mm; anthers oblong, 0.8-1.1 mm. Fruits elliptic-lanceolate, twisted (1 turn or plane, flattened, 6-10 × 2-2.5 mm; valves glabrous or sparsely puberulent, trichomes simple, 0.05-0.15 mm; ovules 14-20 per ovary; style (1-)2-3 mm. Seeds oblong, 1.1-1.4 × 0.7-0.9 mm.

Flowering Jun-Jul. Rocky areas, damp shady ravines, aspen-spruce communities; 1800-3600 m; Ariz.

Draba bifurcata is distinguished from other North American species by a combination of yellow flowers with styles (1-)2-3 mm and almost exclusively simple trichomes on the abaxial surface of cauline leaf blades. It is known only from Chiricahua, Santa Catalina, and White mountains in Apache, Cochise, and Pima counties.


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