Draba paysonii
Contr. Gray Herb. 56: 52. 1918.
Perennials; (cespitose, densely pulvinate); caudex branched (covered with persistent leaves, branches creeping, sometimes terminating in sterile rosettes); scapose. Stems unbranched, 0.05–0.3 dm, densely pubescent throughout, trichomes simple, 0.4–1.3 mm, and stalked, 2–5-rayed, stellate, 0.1–0.6 mm. Basal leaves (imbricate); rosulate; sessile; blade linear to linear-oblanceolate, 0.4–1.2 cm × 0.8–1.5 mm, margins entire, (ciliate, trichomes simple and spurred, (0.4–)0.6–1.4 mm), surfaces pubescent, abaxially (dense) with stalked, 2–12-rayed trichomes, 0.1–0.8 mm, adaxially with simple and 2-rayed ones, 0.3–1 mm, (midvein prominent). Cauline leaves 0. Racemes 2–7-flowered, ebracteate, slightly elongated in fruit; rachis not flexuous, pubescent as stem. Fruiting pedicels divaricate-ascending, straight, 3–9 mm, pubescent, trichomes simple (0.4–1.4 mm), and stalked, 2–5-rayed (0.1–0.6 mm). Flowers: sepals oblong, 2.8–3.5 mm, pubescent, (trichomes simple and short-stalked, 2–4-rayed); petals pale yellow, oblanceolate to spatulate, (4–)5–6 × (1.5–)2–3 mm; anthers oblong, 0.5–0.7 mm. Fruits often broadly ovoid to lanceolate, plane, slightly inflated basally, (5–)6–9 × (3–)3.7–5 mm; valves densely pubescent, trichomes simple and 2-rayed, (0.2–)0.4–1 mm, (occasionally with fewer, smaller, 4- or 5-rayed ones); ovules 8–12 per ovary; style (0.6–)0.8–1.2 mm. Seeds oblong, 1.7–2.2 × 1–1.4 mm.
Phenology: Flowering Jun–Jul.
Habitat: Limestone rock outcrops, talus, gravelly calcareous soil
Elevation: 1800-3500 m
Discussion
Draba paysonii is known from southwestern Montana (Gallatin, Glacier, Madison, and Meagher counties) and northwestern Wyoming (Fremont and Park counties). Reports of its occurrence in Alberta (e.g., G. A. Mulligan 1971b) are based on plants of D. novolympica, a species formerly treated as D. paysonii var. treleasei. Features distinguishing these two species are discussed under 70. D. novolympica.
Selected References
None.