Draba paucifructa |
Draba nivalis |
|
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Charleston Mountain Draba |
snow Draba, snow whitlow-grass, yellow arctic Draba |
|
Habit | Perennials; caudex simple or branched (not fleshy, usually with some persistent leaf remains); sometimes scapose. | Perennials; (cespitose, usually forming mats); caudex branched (covered with persistent leaf bases); usually scapose. |
Stems | unbranched, (0.1–)0.3–0.9 dm, glabrous throughout or sparsely pubescent proximally, trichomes simple and 2–6-rayed, 0.1–0.5 mm. |
unbranched, 0.2–0.8(–1.2) dm, pubescent throughout, trichomes minutely stalked, 8–15-rayed, stellate, (non-crisped), 0.03–0.15 mm. |
Basal leaves | rosulate; petiolate; petiole (0–0.5 cm), ciliate throughout; blade oblanceolate to obovate, 0.4–1.7(–2.3) cm × 1.6–4(–6) mm, margins usually entire, rarely denticulate, (sparsely ciliate, trichomes simple, 0.3–0.8 mm), surfaces pubescent, abaxially with stalked, (2–)4(–6)-rayed trichomes, (0.05–)0.1–0.6 mm, adaxially with simple and fewer, stalked, 2–4-rayed ones. |
rosulate; petiole (obsolete), ciliate throughout; blade oblanceolate to obovate, 0.2–0.9(–1.5) cm × 1–3(–5) mm, margins entire, (not ciliate), surfaces usually pubescent, rarely glabrescent, with short-stalked, 8–15-rayed, stellate, (non-crisped) trichomes, 0.05–0.15 mm. |
Cauline leaves | 0 or 1; sessile; blade ovate to lanceolate, margins entire, surfaces pubescent as basal. |
0 or 1; sessile; blade ovate or oblong, margins entire, surfaces pubescent as basal. |
Racemes | (2–)4–9(–12)-flowered, ebracteate, elongated in fruit; rachis slightly flexuous, glabrous. |
3–9(–11)-flowered, ebracteate, elongated in fruit; rachis often slightly flexuous, pubescent as stem. |
Flowers | sepals ovate, 1.2–1.7 mm, pubescent, (trichomes simple and short-stalked, 2- or 3-rayed); petals yellowish (quickly fading white), spatulate, 1.8–2.2 × 0.6–1 mm; anthers ovate, 0.25–0.3 mm. |
sepals ovate, 1.5–2 mm, pubescent, (trichomes simple and short-stalked, 2–5-rayed); petals white, spatulate to oblanceolate, 2–3.5 × 0.8–1.4 mm; anthers ovate, 0.2–0.3 mm. |
Fruiting pedicels | divaricate-ascending, straight, 2–5(–8) mm, glabrous. |
usually ascending, rarely divaricate, straight, 1–4.5(–8) mm, pubescent as stem. |
Fruits | elliptic to linear lanceolate, plane, flattened, 5–10(–12) × 1.7–2(–2.5) mm; valves glabrous; ovules 20–30 per ovary; style 0.08–0.2 mm. |
elliptic to narrowly oblong-elliptic, twisted or not, flattened, 3.5–9 × 1.5–2.2 mm; valves usually glabrous, rarely with 3–6-rayed trichomes on replum; ovules 12–24(–28) per ovary; style 0.1–0.4 mm. |
Seeds | oblong, 0.9–1.2 × 0.5–0.8 mm. |
ovoid, 0.6–1 × 0.5–0.6 mm. |
2n | = 40. |
= 16. |
Draba paucifructa |
Draba nivalis |
|
Phenology | Flowering Jun–Jul. | Flowering Jun–Aug. |
Habitat | Moist, shaded slopes among limestone and dolomite rocks | Rock outcrops and fellfields, meadows, open tundra, stream banks, gravelly beaches, roadsides |
Elevation | 2600-3500 m (8500-11500 ft) | 0-2500 m (0-8200 ft) |
Distribution |
NV |
AK; AB; BC; MB; NF; NT; NU; ON; QC; YT; Greenland; Europe (Finland, Norway [including Svalbard], n, w Sweden); e Asia (Russian Far East, n Siberia); Atlantic Islands (Iceland); circumpolar |
Discussion | Of conservation concern. Draba paucifructa is known from the Charleston Mountains in Clark County. M. D. Windham (2004) suggested that it is an allopolyploid resulting from hybridization between D. albertina and D. lonchocarpa, and he discussed the morphological features that distinguish this species from its putative parents. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Draba nivalis is most often confused with D. lonchocarpa, and C. L. Hitchcock (1941) reduced the latter to a variety (var. elongata) of D. nivalis. A critical comparison reveals that there are enough differences to warrant their recognition as distinct species. Draba nivalis is distinguished by having non-ciliate leaf bases, basal leaf blades pubescent with trichomes 0.05–0.15 mm, stems and pedicels that are always pubescent, and fruits that are elliptic to narrowly elliptic-oblong, plane, and 3.5–9 mm. By contrast, D. lonchocarpa has ciliate leaf bases, basal leaf blades pubescent with trichomes 0.15–0.5 mm, stems and pedicels that are glabrous or sparsely pubescent, and fruits that are linear to lanceolate or oblong, slightly twisted or plane, and 6–15(–18) mm. Except for Alaska, D. nivalis does not grow in the continental United States, whereas D. lonchocarpa grows in nearly all Mountain and Pacific states. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 327. | FNA vol. 7, p. 322. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | D. caesia | |
Name authority | Clokey & C. L. Hitchcock: Madroño 5: 127. (1939) | Liljeblad: Utkast Sv. Fl., 236. (1792) |
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