Plants: in loose cushions, greenish brown distally, light brown proximally. Stems: to 1 cm, hyalodermis absent, sclerodermis not or weakly differentiated, central strand distinct; axillary hairs to 8 cells long, all hyaline or the proximal one yellow-brown. Stem: leaves crowded, larger distally, appressed and tightly spiraled when dry, weakly spreading when moist, 1–1.4 (plus 0.3–0.6 of awn) mm; ovate to circular, adaxial surface flat to quite concave, base not differentiated; distal margins strongly revolute (to 2 ×), entire or broadly dentate above, cells of revolute margin enlarged, strongly chlorophyllose; apex broadly acute, hyaline in an apical triangle; costa narrow but broader above, excurrent as a hyaline awn, lamina inserted laterally, adaxial outgrowths none, superficial adaxial cells long-rectangular, in 2–4 rows; transverse section rounded, adaxial epidermis present, adaxial stereid band absent, guide cells 2 in 1 layer, hydroid strand present, abaxial stereid band present, rounded in cross-sectional shape, abaxial epidermis absent; basal cells weakly differentiated, rectangular, thin-walled; distal medial cells hexagonal to short-rectangular or rhomboid, rather large, (14–)20–25 µm wide, 1–4:1; papillae absent medially, hollow-papillose on revolute margins, cell walls thin to thickened and porose, superficial abaxial cell walls thick, weakly convex superficially on both sides, cells of leaf apex rhomboid to fusiform, smooth. : Specialized asexual reproduction by brood bodies borne on proximal rhizoids, brown, spheric to elliptic. Sexual: condition polyoicous: synoicous, paroicous, autoicous or perigonia terminal on separate plants. Perichaetia: terminal, interior leaves sheathing, usually differentiated, long-oval, margins usually somewhat differentiated, medial laminal cells rectangular, very thin-walled. Seta: 0.35–0.4 cm. Capsule: stegocarpous, theca elliptic, occasionally weakly ventricose, 1.2–1.5 mm, annulus of 3 rows of smaller, quadrate, highly vesiculose cells; operculum broadly short-conic to long-conic, peristome teeth 32, long, linear, twisted counterclockwise about 1/2 turn. Calyptra: cucullate. Spores: 13–16 µm. KOH laminal color reaction red. Canada, Europe, Asia.
Species 1. Hilpertia is unique among the Pottioideae in the elaboration of a photosynthetic organ consisting of laminal marginal cells rolled in a spiral tube, thin-walled and hollow-papillose. The species is characteristic of cold steppe habitats.