Phytologia 65: 427. 1989 ,.
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 yellowbrown. 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 shortrectangular 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
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.
"um" is not declared as a valid unit of measurement for this property.