Micranthes occidentalis |
Micranthes tenuis |
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mountain saxifrage, redwool saxifrage, western saxifrage |
slender saxifrage |
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Habit | Plants in groups or sometimes almost mat-forming, with bulbils on caudices or rhizomatous. | Plants tufted, with bulbils on caudices. |
Leaves | basal; petiole flattened, 1–5 cm; blade ovate to elliptic, 1.5–3.5 cm, ± fleshy, base ± attenuate to ± truncate, margins shallowly, sharply serrate, ciliate, surfaces sparsely tangled, reddish brown-hairy abaxially, glabrous adaxially. |
basal; petiole broad, flattened, 0.2–1 cm; blade ± obovate to ± obtrullate, 0.5–1.5 cm, ± coriaceous, base ± attenuate to ± cuneate, margins serrate to dentate on distal 1/3–2/3, sometimes ciliate, surfaces glabrous or glabrate abaxially (rarely sparsely reddish brown-hairy). |
Inflorescences | usually (10–)30+-flowered, flowers crowded into 1+ glomerules in thyrses with ascending branches, 8–30 cm, purple-tipped stipitate-glandular; (bracts glabrous or marginally glandular-ciliate). |
usually 2–10-flowered, ± capitate cymes, sometimes solitary flowers, (1–)2–7(–11) cm, hairy or glabrous proximally, glabrate or ± purple-tipped stipitate-glandular distally. (Pedicels proximal ± elongate.) Flowers: sepals erect, ovate to deltate; petals white with purple margins, usually pink or purple tinged, not spotted, obovate to oblong, clawed, 2–3 mm, usually slightly longer than sepals; filaments linear, flattened; pistils connate to 1/2 their lengths; ovary 1/2 inferior, appearing more superior in fruit. |
Flowers | sepals ascending to spreading, sometimes reflexed in fruit, ovate to oblong, (surfaces glabrous); petals white, not spotted (spots rarely present), obovate to almost round, clawed, 2–4 mm, to 1.5 times as long as sepals; filaments linear to very slightly widened near anthers, flattened; pistils distinct almost to base; ovary ± superior. |
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Capsules | greenish or reddish to ± dark purple, folliclelike. |
reddish to purplish, folliclelike. |
2n | = 20, 38, 40, 56, 58. |
= 20. |
Micranthes occidentalis |
Micranthes tenuis |
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Phenology | Flowering spring–summer. | Flowering summer. |
Habitat | Wet, rocky or gravelly slopes, moist to dry alpine meadows, flushes | Open, mossy tundra, rocky ridges, shady ledges |
Elevation | 500-4000 m (1600-13100 ft) | 0-1500 m (0-4900 ft) |
Distribution |
AK; ID; MT; NV; OR; SD; WA; WY; AB; BC; SK
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AK; BC; LB; NT; NU; QC; YT; Greenland; Europe; Asia (Siberia) |
Discussion | Micranthes occidentalis appears closely related to the little-known M. mexicana (Engler & Irmscher) Brouillet & Gornall from Chihuahua, Mexico. The latter is the only species of the genus that occurs in Mexico and not in the United States. Micranthes occidentalis is disjunct between the northern Rocky Mountains and the Cypress Hills of southeastern Alberta and southwestern Saskatchewan, and the Black Hills of South Dakota. It hybridizes with M. idahoensis where their ranges overlap. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Micranthes tenuis is morphologically distinguished from M. nivalis only with great difficulty. D. A. Webb and R. J. Gornall (1989) claimed that chromosome number is one of the chief reasons for continuing to recognize the species and, indeed, their enumeration of morphologic differences is not entirely convincing. Occasionally, both species appear to occur in the same populations. The generally smaller size, tendency to glabrousness, fewer number of flowers, and petal color variations reasonably distinguish M. tenuis. Depauperate specimens of M. nivalis are particularly difficult to separate from M. tenuis except for their very consistent hairiness and white petals. Due to the morphologic confusion, exact distributions are difficult to assess and chromosome number reports may be doubtful (D. L. Krause and K. I. Beamish 1973). A thorough systematic study is needed. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 8, p. 62. | FNA vol. 8, p. 65. |
Parent taxa | Saxifragaceae > Micranthes | Saxifragaceae > Micranthes |
Sibling taxa | ||
Synonyms | Saxifraga occidentalis, Saxifraga allenii, Saxifraga occidentalis var. allenii, Saxifraga occidentalis var. wallowensis, Saxifraga reflexa subsp. occidentalis, Saxifraga saximontana | Saxifraga nivalis var. tenuis, Saxifraga tenuis |
Name authority | (S. Watson) Small: in N. L. Britton et al., N. Amer. Fl. 22: 144. 1905 , | (Wahlenberg) Small: in N. L. Britton et al., N. Amer. Fl. 22: 136. (1905) |
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