Draba arctogena |
Draba exunguiculata |
|
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fellfield whitlowgrass |
clawless Draba |
|
Habit | Perennials; (cespitose); caudex branched (sometimes with persistent leaf remains); sometimes scapose. | Perennials; (densely cespitose); caudex branched (covered with persistent, somewhat thickened, dry petioles); not scapose. |
Stems | unbranched, 0.3–1.4 dm, pubescent throughout, trichomes simple, 0.2–1 mm, and 2–6-rayed, 0.05–0.3 mm. |
unbranched, 0.15–0.7 dm, glabrous throughout or sparsely pubescent, trichomes simple, 0.3–0.9 mm. |
Basal leaves | rosulate; petiolate; petiole base and margin ciliate, (trichomes mostly simple, 0.2–1 mm); blade oblanceolate to narrowly obovate, 0.4–1.7 cm × 1.5–6 mm, margins entire or with 1–3 teeth on each side, surfaces pubescent with primarily simple trichomes, 0.3–1mm, abaxially mixed with stalked, 4–10-rayed ones, 0.1–0.2 mm. |
rosulate; petiolate; petiole ciliate, (trichomes simple, 0.3–1.1 mm); blade linear to linear-oblanceolate, (0.5–)0.8–2(–2.5) cm × 1–3 mm, margins entire, (pubescent as petiole), surfaces abaxially sparsely pubescent with simple and stalked, 2- or 3-rayed trichomes, 0.1–0.4 mm, adaxially glabrous or subapically sparsely pubescent with simple trichomes. |
Cauline leaves | 0 or 1; sessile; blade ovate to oblong, margins entire or toothed, surfaces pubescent as basal. |
1–4; sessile; blade linear to linear-oblanceolate, margins entire, surfaces pubescent as basal. |
Racemes | 2–14(–17)-flowered, ebracteate, elongated in fruit; rachis not flexuous, pubescent as stem. |
4–13(–20)-flowered, ebracteate, elongated in fruit; rachis not flexuous, usually glabrous, rarely sparsely pubescent, trichomes simple, to 1 mm. |
Flowers | sepals ovate, 1.8–2.5 mm, pubescent, (trichomes simple and short-stalked, 2–4-rayed); petals white, spatulate, 3–4 × 1.5–2 mm; anthers ovate, 0.3–0.4 mm. |
sepals ovate, 2–2.5 mm, pubescent, (trichomes simple); petals (erect), yellow, obovate, 2–2.5(–3) × 1.5–2 mm, (not clawed); anthers oblong, 0.6–0.9 mm. |
Fruiting pedicels | suberect to ascending, straight, 1–5(–7) mm, pubescent, trichomes simple and 2–4-rayed. |
divaricate-ascending, straight or slightly curved upward, 1–6 mm, usually glabrous, rarely with few, simple trichomes. |
Fruits | oblong, plane, flattened, 4–9 × 2–3.5 mm; valves pubescent, trichomes short-stalked, 2–4-rayed, 0.1–0.5 mm, sometimes with simple ones; ovules 20–32 per ovary; style 0.1–0.4 mm (stigma distinctly wider than style). |
lanceolate to oblong-lanceolate, plane, flattened, 5–13 × 1.5–3 mm; valves glabrous; ovules 20–24 per ovary; style 0.3–1 mm. |
Seeds | ovoid, 0.7–1 × 0.5–0.6 mm. |
ovoid, 1–1.3 × 0.6–0.8 mm. |
2n | = 48. |
= 56 ± 5. |
Draba arctogena |
Draba exunguiculata |
|
Phenology | Flowering Jun–Jul. | Flowering Jul–Aug. |
Habitat | Scree, sandy hills, gravel flats | Open knolls, talus, gravelly alpine slopes, rocky alpine tundra |
Elevation | 0-450 m (0-1500 ft) | 3600-4300 m (11800-14100 ft) |
Distribution |
NT; NU; Greenland |
CO |
Discussion | Draba arctogena is sometimes confused with D. norvegica, from which it differs by having less elongated fruiting racemes, abaxial leaf surfaces with 4–10-rayed (versus cruciform or, rarely, 2–6-rayed) trichomes, and fruits with 2–4-rayed trichomes, 0.1–0.5 mm, (versus glabrous or with simple and 2–4-rayed trichomes, 0.05–0.25 mm). The limits of D. arctica, D. arctogena, D. cinerea, and D. oblongata need to be critically evaluated in light of molecular and cytological data. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Of conservation concern. Draba exunguiculata occupies alpine areas of Clear Creek, El Paso, Grand, and Summit counties in central Colorado. Draba grayana is found in the same general area; both species are apomicts that occasionally grow sympatrically. Draba exunguiculata is easily distinguished from D. grayana by having stems and fruiting pedicels glabrous or sparsely pubescent with simple trichomes (versus moderately to densely pubescent with simple and 2- or 3-rayed trichomes), and by having erect, non-clawed petals, 2–3 mm and slightly longer than sepals (versus flared, clawed petals 3–4.5 mm and nearly twice as long as sepals). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 292. | FNA vol. 7, p. 306. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | D. groenlandica var. arctogena, D. cinerea var. arctogena | D. chrysantha var. exunguiculata, D. chrysantha |
Name authority | (E. Ekman) E. Ekman: Svensk Bot. Tidskr. 25: 492. (1932) | (O. E. Schulz) C. L. Hitchcock: Revis. Drabas W. N. Amer., 46. (1941) |
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