Draba corymbosa |
Draba mulliganii |
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Baffin bay Draba, Baffin bay whitlow-grass, flat-top Draba |
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Habit | Perennials; (cespitose); caudex branched (with persistent leaves or leaf remains, branches sometimes terminating in sterile rosettes); scapose. | Perennials; (cespitose); caudex branched (with persistent leaves); often 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, 0.3–1.2 dm, glabrous throughout or sparsely pubescent proximally, trichomes short-stalked, 4–10-rayed, (non-crisped). |
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; subsessile or shortly petiolate (petiolar base and proximal margin ciliate with stiff, subsetiform, simple trichomes, 0.3–0.6 mm); blade oblanceolate or lanceolate, 5–9 × 1–2 mm, margins entire, surfaces usually pubescent, abaxially with short-stalked, 8–12-rayed, stellate, (non-crisped) trichomes, 0.1–0.3 mm (often without spurred rays), rarely glabrescent, trichomes confined to margin, (midvein and petiole not thickened), adaxially with similar stellate and some simple trichomes. |
Cauline leaves | 0. |
0. |
Racemes | 2–9(–12)-flowered, ebracteate, (corymbose), slightly elongated in fruit; rachis not flexuous, pubescent as stem. |
3–11-flowered, ebracteate, elongated in fruit; rachis not flexuous, glabrous. |
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 (caducous), ovate, 1.7–2.2 mm, pubescent subapically, (trichomes simple and 2-rayed); petals white, broadly obovate, 3.2–4 × 2–3 mm, (apex obtuse); anthers ovate, 0.4 mm. |
Fruiting pedicels | divaricate-ascending, straight or slightly curved upward, 4–11(–16) mm, pubescent, trichomes simple and 2–4-rayed. |
divaricate to ascending (not appressed to rachis), straight, (4–)5–9 mm, glabrous. |
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-lanceolate to oblong, not twisted, flattened, 5–8 × 2–2.5 mm; valves glabrous; ovules 12–16 per ovary; style 0.4 1 mm. |
Seeds | (brown), ovoid, 1–1.3 × 0.6–0.9 mm. |
ovoid, 0.7–1.1 × 0.5–0.6 mm. |
2n | = 128, 144. |
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Draba corymbosa |
Draba mulliganii |
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Phenology | Flowering Jun–Aug. | Flowering Jun–Jul. |
Habitat | Moist tundra, among calcareous or dolomitic rocks, gravel beaches, silt and clay terraces | Limestone gravel around outcrops, limestone crevices, dry serpentine knolls in heath vegetation with patches of exposed slide rock, shale rubble slopes |
Elevation | 0-1700 m (0-5600 ft) | 300-1600 m (1000-5200 ft) |
Distribution |
AK; BC; NT; NU; YT; Greenland; Europe (Norway, n Russia); e Asia (Russian Far East, Siberia) |
AK |
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.) |
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Source | FNA vol. 7, p. 301. | FNA vol. 7, p. 321. |
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) | Al-Shehbaz: Harvard Pap. Bot. 14: 85. (2009) |
Web links |