Draba scotteri |
Draba borealis |
|
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scotter's whitlowgrass |
boreal Draba, northern Draba, northern whitlow-grass |
|
Habit | Perennials; (cespitose); caudex simple or branched (covered with persistent leaves); scapose. | Perennials; caudex branched (branches usually slender, elongated, rhizomatous, sometimes with persistent leaf bases); not scapose. |
Stems | unbranched, 0.2–1.4 dm, pubescent throughout, trichomes 2–8-rayed, 0.07–0.4 mm, and, sometimes, simple ones, 0.2–0.8 mm. |
usually unbranched, rarely branched, (0.4–)1–3.6(–5.5) dm, often hirsute proximally, trichomes usually simple and 2-rayed, 0.5–1.1 mm, with short-stalked, 3–8-rayed ones, 0.1–0.4 mm (rarely simple trichomes absent distally). |
Basal leaves | rosulate; petiolate; petiole base ciliate, (trichomes simple, 0.2–1 mm); blade oblanceolate, 0.4–1.5 cm × 1–3 mm, margins entire, (ciliate as petiole base), surfaces pubescent with short-stalked, stellate, 8–12-rayed trichomes, 0.1–0.4 mm. |
rosulate; blade ovate or obovate to oblanceolate, (0.5–)1–4.2(–6) cm × 3–10(–25) mm, margins dentate or denticulate, surfaces pubescent, trichomes short-stalked, cruciform, or (2–)4–6-rayed, 0.2–0.6 mm (principal rays usually simple, rarely 1 or 2 with a lateral branch, sometimes appearing to 10-rayed). |
Cauline leaves | 0. |
(2 or) 3–7(–12); sessile; blade ovate, margins entire or dentate, surfaces pubescent as basal or adaxially with some simple trichomes. |
Racemes | 1–9-flowered, usually ebracteate, rarely proximalmost flower subtended by a tiny bract, usually considerably elongated in fruit; rachis not flexuous, pubescent as stem. |
(6–)8–20(–35)-flowered, ebracteate, elongated in fruit; rachis not flexuous, pubescent as stem. |
Flowers | sepals oblong, 2–3 mm, subapically pubescent, (trichomes simple); petals yellow, obovate to spatulate, 3.5–5.5 × 1.5–2.5 mm; anthers ovate, 0.4–0.5 mm. |
sepals ovate, 2–3 mm, pubescent, (trichomes simple); petals white, obovate, 4–6 × 2–3 mm; anthers ovate, 0.3–0.5 mm. |
Fruiting pedicels | divaricate-ascending, straight, 3–8(–12) mm, pubescent as stem. |
divaricate or ascending, straight, (2–)4–8(–13) mm, pubescent as stem. |
Fruits | lanceolate to narrowly so, plane, flattened, 5–11 × 1.5–2.5 mm; valves pubescent, trichomes simple, 0.1–0.4 mm, occasionally with some 2-rayed ones; ovules 12–18 per ovary; style 0.3–1 mm. |
ovate to broadly oblong or lanceolate, slightly twisted or plane, flattened, (5–)7–12 × 2.5–4.5 mm; valves pubescent, trichomes simple and short-stalked, 2–4-rayed, 0.1–0.4 mm; ovules 16–28(–30) per ovary; style 0.2–0.6(–0.8) mm, glabrous. |
Seeds | ovoid, 0.8–1.2 × 0.6–0.7 mm. |
oblong, 1–1.5 × 0.7–1 mm. |
2n | = 96. |
= 64, 80. |
Draba scotteri |
Draba borealis |
|
Phenology | Flowering Jun–Jul. | Flowering Jun–Jul. |
Habitat | Talus and gravelly summits in alpine communities | Rock outcrops and talus, gravelly terraces, meadows, forest edges and thickets, roadsides, grassy areas, alpine tundra |
Elevation | 1200-2000 m (3900-6600 ft) | 0-2400 m (0-7900 ft) |
Distribution |
YT |
AK; AB; BC; NT; NU; YT; e Asia (Japan, Russian Far East) |
Discussion | Of conservation concern. The description of Draba scotteri is based on collections from Kluane National Park, southwestern Yukon Territory. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Draba borealis is highly variable in leaf and stem indumentum, leaf shape and margin, number of cauline leaves, and fruit shape, size, and twisting. North American plants yielded decaploid chromosome counts; octoploid populations were reported from the Russian Far East. This suggests that more than one taxon is present, and the species is much in need of detailed molecular, cytogenetic, and morphological study. In the absence of flowers, Draba borealis is occasionally confused with some forms of D. aurea. The latter usually has proximally bracteate (versus ebracteate) racemes, generally longer styles [0.5–1.5(–1.7) versus 0.2–0.6(–0.8) mm], and more ovules [28–38(–44) versus 16–28(–30)] per ovary. Draba borealis occasionally is confused with D. glabella, but the latter has pectinate-stellate trichomes on abaxial leaf blade surfaces. R. C. Rollins (1993) indicated that D. borealis occurs in Colorado, but we have not seen any material from the United States outside of Alaska. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 335. | FNA vol. 7, p. 296. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | D. borealis var. maxima, D. maxima, D. unalaschkiana | |
Name authority | G. A. Mulligan: Canad. J. Bot. 57: 1874. (1979) | de Candolle: Syst. Nat. 2: 342. (1821) |
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