Mnium roellii Brotherus, Bot. Centralbl. 44: 420. 1890; Bryum sandbergii Holzinger; Roellia lucida Kindberg; R. roellii (Brotherus) A. L. Andrews ex H. A. Crum; R. simplex Kindberg

Stems 1-4 cm. Leaves sometimes tinted pink or red proximally, small and scalelike on proximal portions of stem, enlarged distally, rosette leaves 4-7 mm; laminal cells 90-150 × 30-50 µm; basal cells more regularly rectangular, often somewhat narrower than distal cells; marginal cells narrower, walls thicker, forming somewhat distinct border 1-2 rows wide. Perigonia conspicuous, antheridia abundant, yellow, in disklike heads. Perichaetial leaves similar to stem leaves, smaller. Capsule 4-7 mm.

Capsules mature summer-fall (Jul-Sep). Litter and rich humus under trees and shrubs, montane and subalpine coniferous forests; low to high elevations (0-3200 m); Alta., B.C.; Alaska, Calif., Colo., Idaho, Mont., Nev., Oreg., Utah, Wash., Wyo.

Roellobryon roellii is rare in Alaska, Nevada, and Utah, and is most common in areas south of the Pleistocene ice-sheets in western North America. Coastal Alaskan-northern British Columbia populations probably survived glaciation in refugia. The species has been found near sea level in coastal Alaska but generally occurs at 500-3200 m. Capsules are rare.