Draba corymbosa |
Draba helleriana |
|
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Baffin bay Draba, Baffin bay whitlow-grass, flat-top Draba |
Heller's Draba |
|
Habit | Perennials; (cespitose); caudex branched (with persistent leaves or leaf remains, branches sometimes terminating in sterile rosettes); scapose. | Biennials or perennials; (short-lived); caudex simple or branched; 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). |
branched, (0.1–)1.5–4.3(–5.1) dm, hirsute throughout, trichomes simple, 0.4–1.3(–1.8) mm, with short-stalked to subsessile, 3–5-rayed ones, 0.2–0.4 mm, (some slightly coarser, 2-rayed). |
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 base ciliate or not; blade oblanceolate to obovate, 0.9–4.1(–5.2) cm × 2–7(–10) mm, margins entire or dentate, surfaces pubescent, abaxially with stalked, cruciform, and fewer 3–5-rayed trichomes, 0.1–0.6 mm, adaxially with cruciform and simple trichomes, 0.4–1.3 mm, and smaller 2-rayed ones. |
Cauline leaves | 0. |
(8–)12–31(–43); sessile; blade ovate to lanceolate or oblong, margins usually dentate, rarely subentire, surfaces pubescent as basal. |
Racemes | 2–9(–12)-flowered, ebracteate, (corymbose), slightly elongated in fruit; rachis not flexuous, pubescent as stem. |
10–52(–83)-flowered, usually ebracteate, rarely proximalmost 1 or 2 flowers bracteate, elongated in fruit; rachis not flexuous, 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 oblong, 2.5–4 mm, pubescent, (trichomes simple and stalked, 2-rayed); petals yellow, oblanceolate, 5–7 × 1.5–2.2 mm; anthers oblong, 0.5–0.8 mm. |
Fruiting pedicels | divaricate-ascending, straight or slightly curved upward, 4–11(–16) mm, pubescent, trichomes simple and 2–4-rayed. |
horizontal to divaricate-ascending, straight or slightly curved upward, 4–10(–13) mm, pubescent as rachis abaxially, glabrous adaxially. |
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). |
(not appressed to rachis), lanceolate to ovate or oblong-lanceolate, slightly to strongly twisted or plane, flattened, 5–15 × 2–3.5 mm; valves puberulent, trichomes simple and subsessile, 2(–4)-rayed, 0.03–0.25(–0.8) mm; ovules 14–28 per ovary; style (1–)1.5–3.5 mm. |
Seeds | (brown), ovoid, 1–1.3 × 0.6–0.9 mm. |
oblong, 1–1.3 × 0.6–0.8 mm. |
2n | = 128, 144. |
= 18. |
Draba corymbosa |
Draba helleriana |
|
Phenology | Flowering Jun–Aug. | Flowering Jun–Sep. |
Habitat | Moist tundra, among calcareous or dolomitic rocks, gravel beaches, silt and clay terraces | Oak and pine-fir woodlands, aspen groves, rocky meadows |
Elevation | 0-1700 m (0-5600 ft) | 2100-3600 m (6900-11800 ft) |
Distribution |
AK; BC; NT; NU; YT; Greenland; Europe (Norway, n Russia); e Asia (Russian Far East, Siberia) |
AZ; CO; NM; Mexico (Nuevo León)
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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.) |
Draba helleriana is highly variable and was divided by C. L. Hitchcock (1941) into four varieties. For a discussion of those and the circumscription of the species, see I. A. Al-Shehbaz and M. D. Windham (2007). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 301. | FNA vol. 7, p. 311. |
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 | D. aurea var. tylosa, D. helleriana var. leiocarpa, D. helleriana var. neomexicana, D. helleriana var. patens, D. helleriana var. pinetorum, D. neomexicana, D. neomexicana var. robusta, D. pallida, D. patens, D. pinetorum, D. stylosa |
Name authority | R. Brown ex de Candolle: Syst. Nat. 2: 343. (1821) | Greene: Pittonia 4: 17. (1899) |
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