Draba oligosperma |
Draba crassifolia |
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few-seed Draba, few-seed Draba whitlow-grass, few-seed whitlow-grass |
Rocky Mountain Draba, Rocky Mountain whitlow-grass, snowbed Draba, snowbed whitlow-grass, thick-leaf Draba |
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Habit | Perennials; (cespitose, densely pulvinate); caudex branched (with persistent leaf bases, branches congested or somewhat creeping, sometimes terminating in sterile rosettes); scapose. | Annuals or perennials; (short-lived); caudex branched (when present); usually scapose. |
Stems | unbranched, (0.1–)0.2–0.6(–1) dm, glabrous throughout or pubescent, trichomes sessile, pectinate, 0.1–0.3 mm, (their length parallel to long axis of stem). |
unbranched or, rarely, branched distally, (0.1–)0.3–1.1(–1.5) dm, usually glabrous throughout, rarely pubescent proximally, trichomes simple, 0.3–0.7 mm. |
Basal leaves | rosulate; sessile; blade linear to linear-oblanceolate, (0.2–)0.4–1.1(–1.5) cm × 0.4–1.5(–1.8) mm, margins entire, (not or, rarely, ciliate, trichomes simple, 0.2–0.4 mm), surfaces pubescent with sessile, pectinate trichomes, 0.1–0.4 mm, (their long axis parallel to prominent abaxial midvein), sometimes glabrous adaxially. |
rosulate; petiolate; petiole ciliate throughout; blade oblanceolate to obovate, (0.2–) 0.5–2.5(–3) cm × (1–)2–4(–6) mm, margins usually entire, rarely denticulate, (sometimes ciliate), surfaces glabrous or sparsely pubescent, with simple and 2-rayed trichomes, 0.3–0.9 mm. |
Cauline leaves | 0. |
usually 0, rarely 1; sessile; blade oblong to ovate, margins entire, surfaces glabrous. |
Racemes | 4–12(–17)-flowered, ebracteate, elongated in fruit; rachis not flexuous, glabrous or pubescent as stem. |
(2–)4–15(–25)-flowered, ebracteate, elongated in fruit; rachis slightly flexuous or straight, glabrous. |
Flowers | sepals ovate, 1.5–3 mm, glabrous or sparsely pubescent, (trichomes pectinate, 2-rayed, or simple); petals usually yellow, rarely creamy white, obovate, 2.5–4 × 1.5–3 mm; anthers ovate, 0.4–0.5 mm, (not producing pollen). |
(chasmogamous, petaliferous); sepals (green or purplish), ovate, 1–2 mm, glabrous; petals yellow (often fading white), oblanceolate, 1.5–2.5(–3) × 0.5–1 mm; anthers ovate, 0.15–0.25 mm. |
Fruiting pedicels | divaricate-ascending, straight, (2–)3–10(–13) mm, glabrous or sparsely pubescent, trichomes pectinate. |
horizontal to divaricate-ascending, usually straight, rarely curved upward, 3–8(–10) mm (subequaling or shorter than fruit), glabrous. |
Fruits | ovoid to lanceolate, plane, inflated at least basally, sometimes slightly flattened distally, 3–6(–7) × 2–3.5(–4) mm; valves usually puberulent, rarely glabrous, trichomes simple and sessile, often unequally 2-rayed, 0.07–0.35 mm; ovules 6–12 per ovary; style 0.1–0.8(–1.1) mm. |
usually narrowly elliptic to lanceolate, rarely linear-lanceolate, plane, flattened, (3–)5–10 × 1.5–2.5 mm; valves glabrous; ovules (8–)16–24(–30) per ovary; style 0.02–0.1 mm. |
Seeds | ovoid, 1.1–1.5 × 0.7–1 mm. |
elliptic, 0.7–0.8 × 0.4–0.5 mm. |
2n | = 32, 64. |
= 40. |
Draba oligosperma |
Draba crassifolia |
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Phenology | Flowering May–Jul. | Flowering Jun–Sep. |
Habitat | Rock outcrops, talus, gravel benches, tundra | Rock outcrops and talus, subalpine meadows, alpine summits and tundra, bare snow-melt areas |
Elevation | 200-3900 m (700-12800 ft) | (50-)1000-4300 m ((200-)3300-14100 ft) |
Distribution |
AK; CA; CO; ID; MT; NV; OR; WY; AB; BC; NT; NU; YT
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AK; AZ; CO; ID; MT; NM; NV; UT; WA; WY; AB; BC; LB; NT; NU; QC; YT; Greenland; n Europe (Norway, Sweden)
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Discussion | Draba oligosperma is a highly variable and widespread species that has been shown to be apomictic (G. A. Mulligan and J. N. Findlay 1970; Mulligan 1972). It has been divided into species and infraspecific taxa by previous authors; the variation is continuous in every character; there are no clear geographical and morphological patterns that support its division. For characteristics separating D. oligosperma from the closely related D. pectinipila, see 80. D. pectinipila. Draba andina (Nuttall) A. Nelson (1899), not Philippi (1858) is an illegitimate name, sometimes found in synonymy under D. oligosperma. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
M. D. Windham (2004) presented morphological and chromosomal data suggesting that Draba crassifolia is an allopolyploid produced by hybridization between D. albertina and D. fladnizensis. Although the species is distinctive in large part, some individuals can be difficult to place and there is evidence of rare backcrossing (Windham, unpubl.). The attribution to Arizona is based on Schaack 345 (US) and Kearney & Peebles 12156 (US), both collected on the San Francisco Peaks in Coconino County. Draba crassifolia is found at elevations as low as 50 m in Greenland and the islands of Nunavut. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 324. | FNA vol. 7, p. 302. |
Parent taxa | Brassicaceae > tribe Arabideae > Draba | Brassicaceae > tribe Arabideae > Draba |
Sibling taxa | ||
Synonyms | D. calcifuga, D. oligosperma var. andina, D. oligosperma var. leiocarpa, D. oligosperma var. microcarpa, D. oligosperma var. saximontana, D. oligosperma subsp. subsessilis, D. oligosperma var. subsessilis, D. saximontana, D. subsessilis | D. crassifolia var. parryi, D. parryi |
Name authority | Hooker: Fl. Bor.-Amer. 1: 51. (1830) | Graham: Edinburgh New Philos. J. 7: 182. (1829) |
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