Micranthes idahoensis
Micranthes lyallii
Idaho saxifrage
Lyall's saxifrage, red-stem saxifrage
basal;
petiole flattened, 1–5 cm;
blade ovate to elliptic, 1–4 cm, ± fleshy, base attenuate, margins shallowly serrate to dentate (teeth usually to 1 mm), sparsely ciliate, surfaces tangled, reddish brown-hairy abaxially, glabrate adaxially.
basal;
petiole rounded to flattened, 2–10 cm;
blade spatulate to obovate, 0.8–8 cm, thin, base cuneate to slightly attenuate, margins serrate to dentate, eciliate or sparsely glandular-ciliate, surfaces abaxially glabrous, adaxially sparsely brown-hairy.
15+-flowered, open thyrses, (flowers ± crowded at tips, becoming more open in fruit), 10–40 cm, purple-tipped stipitate-glandular.
usually 10–15-flowered, lax, cylindric thyrses, (red), (4–)7–30 cm, sparsely purple-tipped stipitate-glandular.
sepals reflexed, ovate to oblong;
petals white, with 2 basal yellow spots (often faded when dried), elliptic to ovate, clawed to nearly not clawed, 1–3.5 mm, ± equaling sepals;
filaments club-shaped, not petaloid, (equaling petals);
pistils distinct almost to base;
ovary superior, (to 1/3 adnate to hypanthium).
sepals reflexed, oblong to elliptic;
petals white, each with 2 basal yellowish green spots, elliptic to round, clawed, 2–5.5 mm, longer than sepals;
filaments club-shaped, (to 6 mm);
pistils connate 1/2+ their lengths;
ovary superior, (to 1/3 adnate to hypanthium).
green to reddish purple, folliclelike.
green to yellow, distal 1/2 purple, ± folliclelike, (basally connate).
= 20.
= ca. 56, 58.
Micranthes idahoensis
Micranthes lyallii
Micranthes idahoensis appears to hybridize with M. occidentalis where their ranges overlap. Intermediates are abundant in some populations along the Idaho-Montana border and in Montana. This phenomenon may explain the range of filament shapes found in M. occidentalis, from flattened to sightly club-shaped. The issue of the status of M. idahoensis with respect to M. marshallii (D. L. Krause and K. I. Beamish 1972) is best deferred until a thorough study of the whole complex over its entire range is done.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Although they have nearly disjunct sets of populations, the subspecies of Micranthes lyallii are difficult to distinguish from each other. The more northern plants tend to be larger with wider leaves and often have been called Saxifraga lyallii subsp. or var. hultenii. Apparent hybrids with M. odontoloma occur in Alberta, British Columbia, and northern Idaho, and near Glacier National Park, Montana.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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