Plants mat-forming, (stems trailing, thin, basally slightly woody), with slender, woody caudices. Leaves cauline, proximally crowded; petiole absent; blade elliptic-obovate, 0.8-1.5 cm, fleshy, base cuneate, margins entire, sometimes proximally sparsely long-ciliate, surfaces glabrous. Inflorescences 2-10-flowered, lax cymes, sometimes solitary flowers, 3-12 cm, glabrous or purplish- or pink-tipped stipitate-glandular; (bracts 1-3, proximal). Flowers: sepals erect to spreading, ovate; petals white, not spotted, linear to oblanceolate, 2.5-5 mm, longer than sepals, short- or not clawed; filaments broadly club-shaped (± petaloid); pistils connate to 1/2 their lengths; ovary ± superior (to 1/4 adnate to hypanthium). Capsules green, purple mottled, valvate. 2n = 30.

Flowering summer. Arctic and alpine tundra, fell-fields; 500-4000 m; B.C.; Alaska, Calif., Idaho, Mont., Nev., Oreg., Utah, Wash.

Unlike those of most Micranthes species, the leaves of M. tolmiei are proximally cauline and the ovules have two integuments. The seeds have a loose, winglike testa.