Pleurozium schreberi var. tananae (Grout) Wijk & Margadant
Plants 1--3 mm wide measured across leafy stem, to 16 cm long. Stems reddish, distinctly seen through wet leaves. Stem leaves moderately concave, 1.5--2.8 × 0.8--1.5 mm; median cells 50--100 × 6--9 µm, obviously shorter at extreme apex; alar cells usually orange-brown, slightly enlarged, quadrate to oblong, 18--40 × 12--28 µm. Branch leaves concave, 0.8--1.9 × 0.3--0.8 mm. Seta 15--43 mm. Capsule ellipsoid, 1.5--2.5 mm.
Soil, humus, and rock, often covering the forest floor in extensive mats, in a variety of forest types from dry oak/pine/aspen to wet spruce muskeg; sometimes in bogs, fens, and grass balds; rarely in tundra; 0--3000 m; Greenland; St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld., N.W.T., N.S., Nunavut, Ont., P.E.I., Que., Sask., Yukon; Ala., Alaska, Ark., Colo., Conn., Idaho, Ill., Ind., Iowa, Ky., Maine, Md., Mass., Mich., Minn., Mo., Mont., Nebr., N.H., N.J., N.Mex., N.Y., N.C., Ohio, Oreg., Pa., R.I., S.Dak., Tenn., Vt., Va., Wash., W.Va., Wis., Wyo.; Mexico; Central America; South America; Eurasia; Atlantic Islands.
Pleurozium schreberi is generally a forest dweller and only rarely inhabits Arctic tundra. Arctic specimens often have long, slender, sparsely branched stems. An extreme example is the nomenclatural type of the var. tananae. In addition to the reduced branching and slender stems, its leaves are appressed-imbricate and somewhat smaller than the typical range for the species given in the description above. The distal leaf margins are not much inrolled so the apex appears obtuse to rounded rather than apiculate. I interpret such specimens from Arctic tundra to be rare forms of the species induced by the lower nutrient and harsher climatic conditions present outside of the normal forest habitat.