1. Rhizomnium andrewsianum (Steere) T. J. Koponen, Ann. Bot. Fenn. 5: 143. 1968.
Mnium andrewsianum Steere, Bryologist 61: 175, figs. 1-12. 1958
Plants 1-3(-4) cm. Stems dark red to reddish brown or rarely black when old; micronemata absent. Leaves reddish, reddish brown, or sometimes yellow-green or with golden hue, slightly to moderately contorted when dry, orbicular, broadly elliptic, or occasionally obovate, (1-)1.8-2.4(-3.8) mm; margins reddish, brownish, or rarely green, 1-stratose; apex rounded or occasionally retuse, not apiculate; costa subpercurrent or rarely weakly percurrent; medial laminal cells short-elongate or sometimes ± isodiametric, 45-65(-80) µm, collenchymatous, walls pitted; marginal cells rhomboidal or rectangular, in 1-2(-3) rows. Sexual condition dioicous. Seta 1.5-2 cm. Capsule elliptic, 1.2-2 mm; operculum conic; exostome yellow, lamellae 18+. Spores 25-30 µm.
Capsules mature summer. Wet areas (depressions) in tundra; low elevations; Greenland; Alta., Nfld. and Labr., N.W.T., Nunavut, Yukon; Alaska; Europe; Asia.
Rhizomnium andrewsianum is characterized by diminutive plants with small, reddish to reddish brown, erect leaves, sometimes resembling species of leafy liverworts, especially when mixed with other mosses. The stems are often sinuate at maturity. The leaves are arched with the apex folded upwards towards the stem and margins reflexed when dry, and more or less erect along the stem when moist.