Stereodon vaucheri (Lesquereux) Brotherus
Plants brownish green to golden green, medium-sized, irregularly to somewhat regularly pinnate, creeping to suberect, usually not firmly attached to substrate, 3--6 cm; branches in a single plane, 0.3--1.5 cm. Stems yellowish brown, outermost cells not enlarged, with thin outer walls that collapse inward; pseudoparaphyllia foliose, few, bluntly to sharply toothed on margins. Leaves of stems erect to falcate-secund, 1.2--1.5 × 0.4--0.5 mm, ovate to broadly oblong-lanceolate, gradually to abruptly narrowed to a comparatively short acumen, broadly recurved to almost plane at proximal margin, nearly entire to serrulate distally; costa distinct, single or forked; median cells varying from short to elongate, 30--50 × (3--)4--5(--6) µm, thick and sometimes porose-walled; alar cells shorter and wider and numerous in a well-defined triangular group, with a few enlarged hyaline cells at the basal margin. Sexual condition dioicous; inner perichaetial leaves erect, oblong-lanceolate, plicate, infrequently produced in range of the flora. Seta yellowish to reddish brown, 1--1.5 cm. Capsule brown, inclined, somewhat curved, oblong-cylindric, 1.8--2.2 mm excluding conic operculum, annulus 2--3 seriate; cilia of endostome (1)2--3.
Sporophytes infrequent, capsules mature Aug.--Sept. Generally on rock, especially calcareous rock, but also epiphytic on tree bases, mineral soil, decaying logs, mainly in sunny sites; 0--3500 m; Greenland; Alta., B.C., Man., Nfld., 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; South America; Europe; Asia.
Hypnum vaucheri is widely distributed in boreal and Arctic regions of the Northern Hemisphere. The species 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 median leaf cells are often short elliptic rather than linear-flexuous, especially in leaves that are straight. Hypnum vaucheri is predominantly continental in distribution in North America, while H. cupressiforme is frequent near the coasts.