17. Pohlia filum (Schimper) Mårtenssen, Kungl. Svenska Vetenskapsakad. Avh. Naturskyddsarenden. 14: 149. 1956.
Bryum filum Schimper, Syn. Musc. Eur. ed. 2, 470. 1876
Plants small to medium-sized, green to light green, glossy. Stems 0.5-4 cm. Leaves erect, lanceolate, 0.6-1.2 mm; margins serrulate to serrate in distal 1/3; costa subpercurrent; distal medial laminal cells rhombic to rhomboidal, 35-95 µm, walls thin. Specialized asexual reproduction usually present when sterile; axillary gemmae 1 (or 2), bulbiform, oblong or elliptic to subglobose, green to yellow, black when old, leaf primordia restricted to apex or rarely 1 or 2 proximally, laminate, . Sexual condition dioicous; perigonial leaves ovate; perichaetial leaves scarcely differentiated, lanceolate. Seta orange-brown. Capsule inclined 95-180°, brown to stramineous, pyriform, neck 1/3 urn length; exothecial cells short-rectangular, walls sinuate; stomata superficial; annulus present; operculum convex-conic; exostome teeth yellow-brown, narrowly triangular-acute; endostome hyaline, basal membrane 1/2 exostome length, segments distinctly keeled, broadly perforate, cilia short to rudimentary. Spores 16-23 µm, finely roughened.
Capsules mature summer (Jun-Aug). Gravelly, organic-poor soil, glacial outwash, roadsides; low to high elevations; Greenland; Alta., B.C., N.W.T., Nunavut, P.E.I., Que., Sask.; Alaska, Oreg.; Europe.
Pohlia filum is an easily recognized species characterized by erect, somewhat glossy leaves, and ovoid gemmae that normally arise singly in the leaf axils. The gemmae have a few small, triangular, rather stiff leaf primordia at the apex, rarely with one or two primordia proximal on the gemma body. The gemmae of P. drummondii are more elongate-cylindric and branchlike, with larger, flexuose, often green leaf primordia at the apex and also frequently more proximally on the gemma body.