Mnium triquetrum Linnaeus ex Jolyclerc, Syst. Sex. Vég., 749. 1803

Plants 0.1-1.2 cm. Stem leaves contorted when dry, wide-spreading and distinctly 3-ranked when moist, ovate-lanceolate, 1.5-4 mm; base decurrent; margins plane to weakly reflexed proximally, serrulate distally; apex acute; costa narrow, ending in or just before apex; inner laminal cells smaller, walls thicker than marginal cells. Sexual condition dioicous. Seta 3-10 cm. Capsule 3-4.5 mm. Spores 33-38 µm.

Rich fens, arctic and boreal areas; moderate to high elevations; Greenland; Alta., B.C., Man., Nfld. and Labr., N.W.T., Nunavut, Ont., Que., Yukon; Alaska, Calif., Mich., Minn., Mont., Nebr., N.J., N.Y., Oreg., S.Dak., Vt.; n Eurasia.

Meesia triquetra is frequent where appropriate habitat is available, and disjunct in a few locations farther south. The species is usually easily distinguished by its three-ranked, widely spreading leaves that have serrulate margins.