Kungl. Svenska Vetenskapsakad. Avh. Naturskyddsärenden 14: 149. 1956.
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, small, stiff. 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.
Phenology: Capsules mature summer (Jun–Aug).
Habitat: Gravelly, organic-poor soil, glacial outwash, roadsides
Elevation: 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.