Dryas hookeriana |
Dryas octopetala |
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Hooker's mountain-avens, mountain avens, white dryas, White Mountain-avens |
eightpetal mountain-avens, white dryas, White Mountain-avens |
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Habit | Plants 1.5–9 cm. | Plants 2.5–12 cm. |
Leaf | blades usually oblong-elliptic to lanceolate, sometimes ovate, 4–16(–25) × 1–6(–10) mm, base usually truncate or cordate, sometimes cuneate, margins strongly revolute to flat, coarsely dentate or serrate, sinuses 5–25(–30)% to midvein, apex acute to obtuse, surfaces smooth to slightly plicate, only midvein ± obscured adaxially within medial fold, abaxial tomentose to woolly (obscuring lateral veins), adaxial usually glabrous, sometimes sparsely hairy proximally on midvein, feathery hairs usually absent, rarely 1+ on midveins abaxially, midveins and petioles abaxially stipitate-glandular. |
blades oblong or ovate to elliptic, 3–16 × 0.5–6.5 mm, base usually truncate or cordate, sometimes cuneate, margins flat, coarsely dentate to serrate, sinuses 5–50(–65)% to midvein, apex acute to rounded, surfaces plicate along midvein, usually rugulose, sometimes rugose, midvein and lateral veins sunken, abaxial tomentose to woolly, adaxial usually glabrous, rarely tomentose or sparsely hairy proximally on midvein, feathery hairs scattered to rare along midveins abaxially and on petioles, scattered to rare elsewhere, midveins and petiole apices usually abaxially stipitate-glandular. |
Peduncles | 10–30 mm. |
11–125 mm. |
Flowers | erect at flowering; sepals lanceolate to narrowly elliptic, 4–10 × 0.6–1.5 mm; petals 8, spreading, usually white or cream, sometimes yellow, 9–14 × 5–11 mm; filaments glabrous. |
erect at flowering; sepals linear-oblong, 4–7 × 1.5–2.5 mm; petals 8, spreading, white or cream, 9–14 × 5–9 mm; filaments glabrous. |
Achenes | 2.5–3 mm; styles 11–25 mm. |
2.5–3 mm; styles 16–32 mm. |
2n | = 18. |
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Dryas hookeriana |
Dryas octopetala |
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Phenology | Flowering Jun–Aug. | Flowering Jun–Aug. |
Habitat | Alpine meadows, dry rocky slopes and ridges, alpine tundra | Tundra |
Elevation | 1500–3900 m (4900–12800 ft) | 1000 m (3300 ft) |
Distribution |
AK; CO; ID; MT; OR; UT; WA; WY; AB; BC; NT
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Greenland
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Discussion | In some states and provinces, the distribution of Dryas hookeriana is restricted to northwestern and central Colorado, southeastern and northernmost Idaho, western and central Montana, northeastern Utah (Uinta and Wasatch mountains), eastern Oregon and Washington, southwestern and central Wyoming, and western Northwest Territories. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
On Greenland, a major zone of hybridization and introgression of Dryas octopetala with D. integrifolia occurs, mixing morphological characteristics so extensively as to nearly obliterate D. octopetala (E. Hultén 1971). M. Phillip and H. R. Siegismund (2003) found continuous variation, making a clear separation of the two species impossible. N. Tremblay and D. Schoen (1999) described a series of events isolating populations of Dryas species in refugia during glaciation followed by secondary contact between species after glacial retreat; such events could explain the large amount of variability seen on much of Greenland. Such hybridization and diversification are not uncommon in arctic species (Phillip and Siegismund) and were too recent to allow fixation of consistent characteristics throughout the range of taxa (I. Nordal et al. 1999). Phenotypically, some plants of the eastern coast of Greenland seem to be outliers of Dryas octopetala in the strict sense (T. T. Elkington 1965). Introgressed plants on Greenland have been called D. chamissonis Sprengel ex Juzepczuk (formerly D. chamissonis Jurtzev). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 9, p. 329. | FNA vol. 9, p. 330. |
Parent taxa | Rosaceae > subfam. Dryadoideae > tribe Dryadeae > Dryas | Rosaceae > subfam. Dryadoideae > tribe Dryadeae > Dryas |
Sibling taxa | ||
Synonyms | D. octopetala var. angustifolia, D. octopetala subsp. hookeriana, D. octopetala var. hookeriana | |
Name authority | Juzepczuk: Izv. Glavn. Bot. Sada S.S.S.R. 28: 325. (1929) | Linnaeus: Sp. Pl. 1: 501. (1753) |
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