Draba cana |
Draba sphaeroides |
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Brewer's Draba, canescent Draba, canescent whitlow-mustard, cushion Draba, hoary Draba, hoary whitlow-grass, lance-leaf Draba, lance-leaf whitlow-grass |
ball Draba |
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Habit | Perennials; caudex simple or branched (branches short); not scapose. | Perennials; (cespitose, densely pulvinate); caudex branched (branches often tangled with persistent leaf remnants, prostrate, slender, sometimes terminating in sterile rosettes); scapose. |
Stems | unbranched or branched distally, (0.6–)1–3(–3.8) dm, pubescent throughout, trichomes simple, 0.5–1mm, with 4–10-rayed ones, 0.05–0.2 mm (mostly branched on basal parts). |
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 ciliate throughout; blade linear to oblanceolate or oblong, (0.5–)0.8–2(–3.5) cm × 1.5–4(–11) mm, margins entire or dentate, (base and apex ciliate, trichomes simple, 0.3–0.8 mm), surfaces pubescent with short-stalked, 4–12-rayed trichomes, 0.1–0.3 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 | 3–10(–17), (not overlapping); sessile; blade lanceolate to ovate or oblong, margins entire or dentate, surfaces pubescent as basal (adaxially with simple and forked trichomes near blade base). |
0. |
Racemes | (10–)15–47(–63)-flowered, basally bracteate, often considerably elongated in fruit; rachis not flexuous, densely pubescent, trichomes 4–10-rayed (0.05–0.2 mm), and fewer simple ones. |
(3–)5–11(–14)-flowered, ebracteate, slightly elongated in fruit; rachis not flexuous, glabrous or sparsely pubescent as stem. |
Flowers | sepals (green or lavender), oblong to ovate, 1.5–2 mm, pubescent, (trichomes simple and few-rayed); petals white, oblanceolate to spatulate, 2.3–3.7(–4.5) × 0.7–1.7 mm; anthers ovate, 0.1–0.2 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 or ascending, straight, 2–5(–10) mm, pubescent as rachis. |
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 | (subappressed to rachis), linear-lanceolate to linear or, rarely, ovate-oblong, slightly twisted or plane, flattened, (5–)6–11 × 1.5–2(–2.5) mm; valves pubescent, trichomes short-stalked, 3–7-rayed, 0.05–0.3 mm; ovules 28–48 per ovary; style 0.1–0.6 mm. |
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, 0.5–0.7(–0.9) × 0.3–0.5 mm. |
oblong, 1–1.5 × 0.8–1 mm. |
2n | = 32. |
= 20. |
Draba cana |
Draba sphaeroides |
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Phenology | Flowering (May-)Jun–Aug. | Flowering Jun–Aug. |
Habitat | Rock outcrops and talus, open prairie benchlands, roadsides, meadows, alpine tundra | Rock outcrops, talus, soil pockets on rocky slopes |
Elevation | 0-4100 m (0-13500 ft) | 2500-3300 m (8200-10800 ft) |
Distribution |
AK; CA; CO; ID; ME; MI; MT; NH; NM; NV; SD; UT; VT; WA; WI; WY; AB; BC; MB; NB; NF; NT; ON; QC; SK; YT; Greenland
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NV |
Discussion | The limits of Draba cana have long been confused, and the species was treated as a synonym of the Himalayan D. lanceolata Royle (M. L. Fernald 1934; C. L. Hitchcock 1941) or as a variety of the western North American D. breweri (R. C. Rollins 1993). However, G. A. Mulligan (1971) clearly demonstrated that all three are distinct and should be maintained. Some Utah plants corresponding to the type of D. valida have shorter and wider oblong-ovate fruits. In all other aspects, they are indistinguishable from D. cana. Additional studies are needed to establish whether such plants should be formally recognized. (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. 298. | FNA vol. 7, p. 339. |
Parent taxa | Brassicaceae > tribe Arabideae > Draba | Brassicaceae > tribe Arabideae > Draba |
Sibling taxa | ||
Synonyms | D. breweri var. cana, D. valida | D. oligosperma var. sphaeroides |
Name authority | Rydberg: Bull. Torrey Bot. Club 29: 241. (1902) | Payson: Amer. J. Bot. 4: 265. (1917) |
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