Hypnum complexum (Mitten) A. Jaeger & Sauerbeck; H. subcomplexum Kindberg; Stereodon vaucheri (Lesquereux) Brotherus

Plants medium-sized, brownish to golden green. Stems 3-6 cm, yellowish brown, creeping to suberect, irregularly to somewhat regularly pinnate, branches 0.3-1.5 cm; hyalodermis absent, central strand present; pseudoparaphyllia broadly foliose. Stem leaves erect to falcate-secund, ovate to broadly oblong-lanceolate, gradually to abruptly narrowed to apex, 1.2-1.5 × 0.4-0.5 mm; base not auriculate; margins broadly recurved to almost plane basally, nearly entire to serrulate distally; acumen comparatively short; costa distinct, single or 2-fid; alar cells , region well defined, , with few enlarged hyaline cells at basal margin; basal laminal cells shorter, somewhat wider than medial cells, unpigmented, walls pitted; medial cells 30-50 × (3-)4-5(-6) µm, . Sexual condition dioicous; . Seta yellowish to reddish, 1-1.5 cm. Capsule inclined, brown, oblong-cylindric, 1.8-2.2 mm; annulus 2- or 3-seriate; operculum conic; endostome cilia (1-)2-3.

Capsules mature Aug-Sep. Rock, especially calcareous, epiphytic on tree bases, mineral soil, decaying logs, mainly sunny sites; low to high elevations (0-3500 m); Greenland; Alta., B.C., Man., Nfld. and Labr., N.W.T., Nunavut, Ont., Que., Sask., Yukon; Alaska, Ariz., Ark., Calif., Colo., Minn., Mont., Nebr., Nev., N.Mex., N.Y., N.Dak., S.Dak., Tex., Utah, Wash., Wyo.; Mexico (Coahuila, Nuevo León); South America; Europe; Asia.

Hypnum vaucheri is widely distributed in boreal and Arctic regions of the Northern Hemisphere; the plants are usually not firmly attached to the substrate, and sporophytes are infrequent; the branches emerge in one plane; the stem epidermal cells are not enlarged, with thin outer walls collapsing inward; the pseudoparaphyllia are few, with bluntly to sharply toothed margins; and the alar cells are shorter and wider than the laminal cells, in a triangular region. Hypnum vaucheri is readily confused with H. cupressiforme; the most reliable distinguishing feature is the blunt foliose pseudoparaphyllia of the former (filamentous to lanceolate in H. cupressiforme); in H. vaucheri the medial laminal cells are often short-elliptic rather than linear-flexuous, especially in straight leaves. Hypnum vaucheri is predominantly continental in distribution in North America, while H. cupressiforme is frequent near the coasts.