Draba aureola |
Draba argyrea |
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alpine whitlow-grass, golden alpine Draba, golden Draba, great alpine whitlow-grass, Mt. Lassen Draba, Mt. Lassen Draba whitlow-grass, Mt. Lassen whitlow-grass |
silver Draba |
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Habit | Perennials; (short-lived); caudex simple or branched (poorly developed, with persistent dry leaves); not scapose. | Perennials; caudex branched (branches loose, creeping, sometimes terminating in sterile shoots); scapose. |
Stems | unbranched or branched, 0.3–1.5 dm, hirsute throughout, trichomes simple and long-stalked, 2–4-rayed, 0.2–1.5 mm. |
unbranched, (0.2–)0.3–0.8(–1.1) dm, pubescent proximally, glabrous distally, trichomes short-stalked to subsessile, 5–8-rayed, 0.05–0.2 mm. |
Basal leaves | (forming dense clusters); rosulate; sessile; blade oblanceolate to linear, (0.7–)1–2.5(–3.2) cm × 2–3.5(–5) mm, margins entire, (ciliate, trichomes simple and 2-rayed, 0.5–1.5 mm), surfaces densely hirsute, abaxially with stalked, 3–5-rayed trichomes, 0.1–0.5 mm, adaxially with simple and long-stalked, 2-rayed trichomes, to 1 mm, with smaller, 3–5-rayed ones. |
rosulate; subsessile; petiole base and margin not ciliate, (midvein obscure abaxially); blade oblanceolate to obovate, 0.3–0.7(–1.2) cm × 1–2.5(–4) mm, margins entire, surfaces canescent with short-stalked, 8–12-rayed, stellate trichomes, 0.1–0.2 mm. |
Cauline leaves | 5–33; sessile; blade oblong to linear, margins entire, surfaces pubescent as basal. |
0. |
Racemes | 12–83-flowered, ebracteate or proximalmost 1–9 flowers bracteate, slightly or not elongated in fruit; rachis not flexuous, hirsute as stem. |
2–8(–12)-flowered, ebracteate, elongated in fruit; rachis slightly flexuous, usually glabrous, rarely sparsely pubescent as stem. |
Flowers | sepals ovate, 2.5–4 mm, glabrous; petals bright yellow, linear to linear-oblanceolate, 4–6 × 0.5–1(–1.2) mm; anthers narrowly oblong, 0.8–1 mm. |
sepals ovate, 2–3 mm, pubescent, (trichomes 4–6-rayed); petals yellow, oblanceolate, 4–6 × 1.5–3 mm; anthers ovate, 0.5–0.6 mm. |
Fruiting pedicels | horizontal to divaricate, usually straight, rarely curved upward, (3–)5–12(–19) mm, hirsute as stem. |
divaricate-ascending, straight or slightly curved upward, (4–)5–12(–19) mm, glabrous. |
Fruits | oblong or, rarely, oblong-ovate, plane, flattened, (6–)9–14(–16) × 3–5 mm; valves pubescent, trichomes stalked, 2–4-rayed, 0.07–0.5 mm; ovules 10–20 per ovary; style (0.6–)1–1.6(–2) mm. |
lanceolate to elliptic or ovate, plane or slightly twisted, flattened, 5–11 × 2–3.5(–4.5) mm, (symmetric); valves often puberulent, sometimes glabrous, trichomes simple and subsessile, 2–4-rayed, 0.03–0.2 mm; ovules 8–14 per ovary; style (0.7–)1–1.8(–2.4) mm. |
Seeds | oblong, 1.4–1.9 × 0.8–1.1 mm. |
oblong, 1.2–1.8 × 0.8–1.1 mm. |
2n | = 20. |
= 36. |
Draba aureola |
Draba argyrea |
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Phenology | Flowering Jul–Aug. | Flowering Apr–Jul. |
Habitat | Open conifer forests, alpine meadows and moraines, talus slopes | Rock crevices, ledges, talus slopes |
Elevation | 2200-3200 m (7200-10500 ft) | 1000-3100 m (3300-10200 ft) |
Distribution |
CA; OR; WA
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ID |
Discussion | Draba aureola is known from Lassen, Shasta, and Siskiyou counties in California, Deschutes County in Oregon, and Lewis and Pierce counties in Washington. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
M. A. Beilstein and M. D. Windham (2003) hypothesized that Draba argyrea is an allopolyploid derived through hybridization between D. lonchocarpa and D. sphaerocarpa. The species is restricted to Blaine, Boise, Custer, and Elmore counties in central Idaho. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 295. | FNA vol. 7, p. 292. |
Parent taxa | Brassicaceae > tribe Arabideae > Draba | Brassicaceae > tribe Arabideae > Draba |
Sibling taxa | ||
Synonyms | D. aureola var. paniculata | D. argyrea var. glabrescens |
Name authority | S. Watson: in W. H. Brewer et al., Bot. California 2: 430. (1880) | Rydberg: Bull. Torrey Bot. Club 30: 251. (1903) |
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