Draba corymbosa |
Draba weberi |
|
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Baffin bay Draba, Baffin bay whitlow-grass, flat-top Draba |
weber's Draba |
|
Habit | Perennials; (cespitose); caudex branched (with persistent leaves or leaf remains, branches sometimes terminating in sterile rosettes); scapose. | Perennials; (cespitose); caudex branched (covered with persistent, somewhat thickened, petioles); not scapose. |
Stems | unbranched, (0.05–)0.2–0.8(–1.5) dm, pubescent throughout, trichomes simple and 2-rayed, 0.4–1 mm, with 3–5-rayed ones, 0.05–0.4 mm, (sometimes trichomes mostly simple). |
unbranched, 0.2–0.6(–1) dm, glabrous or sparsely pubescent throughout, trichomes simple, sessile or subsessile, 2- or 3-rayed, 0.2–0.6 mm. |
Basal leaves | rosulate; petiolate; petiole base and margin ciliate, (trichomes often course, simple, 0.4–1.3 mm); blade oblanceolate to obovate, 0.6–1.8 cm × 1.5–5 mm, margins entire, surfaces pubescent, abaxially with stalked, 2–6-rayed trichomes, 0.2–0.6 mm, adaxially with primarily simple and stalked, 2-rayed trichomes, to 1.1 mm, with 3–5-rayed ones, 0.2–0.4 mm. |
rosulate; petiolate; petiole margin ciliate, (trichomes simple, 0.2–0.6 mm); blade linear-oblanceolate, 0.4–1.5 cm × 0.8–1.7 mm, margins entire, (pubescent as petiole), surfaces pubescent abaxially with (appressed), simple, subsessile or sessile, 2–4-rayed trichomes, 0.1–0.4 mm, glabrous or subapically sparsely pubescent adaxially with simple trichomes. |
Cauline leaves | 0. |
1–3; sessile; blade linear-oblong, margins entire, surfaces pubescent as basal. |
Racemes | 2–9(–12)-flowered, ebracteate, (corymbose), slightly elongated in fruit; rachis not flexuous, pubescent as stem. |
5–15-flowered, ebracteate, elongated in fruit; rachis not flexuous, glabrous or pubescent as stem. |
Flowers | sepals (grayish green), broadly ovate, 2.2–3 mm, pubescent, (trichomes simple, to 1 mm, sometimes with stalked, smaller, 2–4-rayed ones); petals (broadly patent), yellow, obovate, 4–6 × 3–5 mm; anthers ovate, 0.3–0.4 mm. |
sepals ovate, 1.5–2 mm, pubescent, (trichomes simple and 2-rayed); petals yellow, spatulate, 3–4 × 1.2–1.8 mm, (flared, clawed); anthers ovate, 0.3–0.4 mm. |
Fruiting pedicels | divaricate-ascending, straight or slightly curved upward, 4–11(–16) mm, pubescent, trichomes simple and 2–4-rayed. |
divaricate-ascending, straight, 2–6 mm, glabrous or sparsely pubescent as stem. |
Fruits | oblong or ovate, plane, flattened, 6–12 × 3.5–5.5 mm; valves pubescent or puberulent, trichomes simple, 0.1–0.4 mm, (sometimes with short-stalked, 2- or 3-rayed ones); ovules 12–24 per ovary; style 0.6–1 mm (stigma distinctly wider than style). |
ovate, plane, flattened, 4–8 × 2–3 mm; valves glabrous; ovules 16–18 per ovary; style 0.2–0.3 mm. |
Seeds | (brown), ovoid, 1–1.3 × 0.6–0.9 mm. |
ovoid, 1–1.2 × 0.6–0.7 mm. |
2n | = 128, 144. |
|
Draba corymbosa |
Draba weberi |
|
Phenology | Flowering Jun–Aug. | Flowering Jun–Jul. |
Habitat | Moist tundra, among calcareous or dolomitic rocks, gravel beaches, silt and clay terraces | Rock crevices along streamlets near timberline |
Elevation | 0-1700 m (0-5600 ft) | ca. 3500 m (ca. 11500 ft) |
Distribution |
AK; BC; NT; NU; YT; Greenland; Europe (Norway, n Russia); e Asia (Russian Far East, Siberia) |
CO |
Discussion | Draba corymbosa, which is 16-ploid or 18-ploid with x = 8, is an extremely variable species of polyphyletic, allopolyploid origin. Most individuals appear to have decaploid D. alpina (2n = 80) in their parentage, but the other genomes are provided by hexaploid (2n = 48) and octoploid (2n = 64) species (C. Brochmann et al. 1993). O. E. Schulz reduced D. corymbosa to a variety of D. alpina; R. C. Rollins (1993) treated it as a distinct species. Draba corymbosa is distinguished from D. alpina by having pubescent or puberulent (versus glabrous or glabrescent) fruits, corymbose (versus usually elongated) fruiting racemes, and abaxial leaf blade surfaces always lacking (versus usually with some) simple trichomes. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Of conservation concern. Draba weberi is an apomictic species allied to D. exunguiculata, D. grayana, and D. streptobrachia. From those, it is distinguished by having ovate fruits, clawed petals, and sessile, 2–4-rayed trichomes with untwisted rays often appressed to leaf and stem surfaces. Draba weberi is known from near North Star Peak in central Colorado (Summit County). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 301. | FNA vol. 7, p. 346. |
Parent taxa | Brassicaceae > tribe Arabideae > Draba | Brassicaceae > tribe Arabideae > Draba |
Sibling taxa | ||
Synonyms | D. alpina var. bellii, D. alpina var. corymbosa, D. barbata, D. bellii, D. kjellmanii, D. macrocarpa, D. vestita | |
Name authority | R. Brown ex de Candolle: Syst. Nat. 2: 343. (1821) | R. A. Price & Rollins: Harvard Pap. Bot. 1(3): 75, fig. 3. (1991) |
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