Draba arctogena |
Draba sphaeroides |
|
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fellfield whitlowgrass |
ball Draba |
|
Habit | Perennials; (cespitose); caudex branched (sometimes with persistent leaf remains); sometimes scapose. | Perennials; (cespitose, densely pulvinate); caudex branched (branches often tangled with persistent leaf remnants, prostrate, slender, sometimes terminating in sterile rosettes); 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, (0.2–)0.3–0.8 dm, sparsely pubescent proximally, glabrous distally, trichomes usually 2- or 3-rayed, rarely some simple, 0.1–0.25 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. |
not rosulate; subsessile; petiole margins not ciliate; blade oblanceolate to oblong or elliptic, 0.3–0.8(–0.9) cm × (1–)1.5–3(–4) mm, margins entire, (not ciliate), surfaces usually pubescent, rarely both surfaces glabrous (except margin), with stalked, 2–4-rayed trichomes, 0.07–0.4 mm (or, rarely, trichomes mostly simple and 2-rayed adaxially). |
Cauline leaves | 0 or 1; sessile; blade ovate to oblong, margins entire or toothed, surfaces pubescent as basal. |
0. |
Racemes | 2–14(–17)-flowered, ebracteate, elongated in fruit; rachis not flexuous, pubescent as stem. |
(3–)5–11(–14)-flowered, ebracteate, slightly elongated in fruit; rachis not flexuous, glabrous or sparsely pubescent as stem. |
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 broadly ovate, 1.7–2.5 mm, glabrous or sparsely pubescent, (trichomes simple and short-stalked, 2- or 3-rayed); petals yellow, spatulate, 2.7–4 × 1.5–2.2 mm; anthers ovate, 0.4–0.5 mm. |
Fruiting pedicels | suberect to ascending, straight, 1–5(–7) mm, pubescent, trichomes simple and 2–4-rayed. |
divaricate-ascending, straight or curved upward, (sometimes slightly expanded basally), 3–8 mm, usually glabrous, rarely sparsely pubescent, trichomes simple and 2- or 3-rayed. |
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). |
broadly lanceolate to ellipsoid or ovoid, plane, inflated at least basally, (2.5–)3.5–7(–8) × (1.5–)2–3.5 mm; valves glabrous or sparsely pubescent, trichomes simple and short-stalked, 2(–4)-rayed, 0.07–0.2 mm; ovules 4–10(–12) per ovary; style 0.3–1(–1.3) mm. |
Seeds | ovoid, 0.7–1 × 0.5–0.6 mm. |
oblong, 1–1.5 × 0.8–1 mm. |
2n | = 48. |
= 20. |
Draba arctogena |
Draba sphaeroides |
|
Phenology | Flowering Jun–Jul. | Flowering Jun–Aug. |
Habitat | Scree, sandy hills, gravel flats | Rock outcrops, talus, soil pockets on rocky slopes |
Elevation | 0-450 m (0-1500 ft) | 2500-3300 m (8200-10800 ft) |
Distribution |
NT; NU; Greenland |
NV |
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 sphaeroides is closely related to D. pedicellata; the two are easily distinguished using the characteristics discussed by M. D. Windham (2004). The species is known from Elko County (East Humboldt, Ruby and Jarbidge mountains) in northeastern Nevada. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 292. | FNA vol. 7, p. 339. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | D. groenlandica var. arctogena, D. cinerea var. arctogena | D. oligosperma var. sphaeroides |
Name authority | (E. Ekman) E. Ekman: Svensk Bot. Tidskr. 25: 492. (1932) | Payson: Amer. J. Bot. 4: 265. (1917) |
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