Nat. Pfl. 1: 547. 1903. -- Webera cardotii Ren. in Ren. & Card., Rev. Bryol. 15: 71. 1888. -- Bryum commutatum asp. cardotii (Ren. in Ren. & Card.) Kindb., Eur. N. Am. Bryin. 2: 388. 1897.
Pohlia porosa H. Lindb., Bull. Torr. Bot. Club 27: 318. 21. 1900. -- Webera porosa (H. Lindb.) Par. Ind. Bryol. ed. 2. 5: 120. 1906.
Plants erect in green to olive green tufts, to 2.5 cm high. Leaves closely imbricated, erect and appressed when dry but erect spreading when moist, concave, lanceolate to ovate-lanceolate with blunt apices, to 1.5 mm long, about 3–3.5: 1, not plicate. Median laminal cells rhomboidal with rather thick walls (lumen: wall ratio about 6: 1) 7–10: 1, smooth, not or lightly pitted, to 10 µm wide. Leaf lamina, especially near the costa, mostly with bistratose streaks. Basal and alar cells little differentiated from median cells. Cells near leaf apex somewhat shorter elliptic than median cells, 2–4: 1, with scattered cells distally slightly prorate. Margins not decurrent, recurved almost to leaf apex, minutely serrulate with right-angled teeth. Limbidium absent, unistratose throughout. Costa flattened at least near base, about 3 times as broad as deep, filling about 1/4 of leaf base, tapering above, green throughout, ending in the obtuse to bluntly acute leaf apex. Costa cross-section with poorly defined ad- and abaxial epidermis, with a single layer of guide cells, with a large abaxial band of stereid or substereid cells and with only a few substereid cells adaxially. Axillary hairs to 4–5 cells long, to 120 µm, with 2 basal brown cells and 2–3 rectangular and thin walled distal cells which are of markedly larger diameter than the basal cells. Rhizoids to 15 µm wide at insertion, papillose, brown to pale brown, sparingly branched, surrounding an isodiametric macronematal area to 100 µm wide. Stem cross-section round, with a conspicuous central strand, with the hyaline and leptodermous inner corticals abruptly transitting to a single layer of only moderately pachydermous, red brown outer cortical cells, without a hyaloderm. Gemmae absent. Annulus of 2–3 rows of very thick-walled cells.
Dioicous. Perichaetial leaves undifferentiated or with few very small leaves hidden within the perichaetium. Seta red-brown, smooth, erect, to 15 mm long. Urn to 5 mm long, cylindric, 4–5: 1, erect to slightly inclined, neither sulcate nor strumose. Operculum short conic to almost dome-shaped. Exothecial cells at capsule mouth to 12 µm broad, rounded isodiametric in 2–3 rows. Exothecial cells at middle of urn isodiametric to short rectangular, 1–2.5: 1, mostly with sinuose lateral walls and oblique transverse walls, to 25 µm broad, not in regular rows, evenly thick walled with lumen: wall ratio 4–6: 1. Stomates phaneroporous, restricted to neck of capsule, raised on short pustules, somewhat longer than broad. Exostome pale to yellow-brown, to 300 µm long, inconspicuously shouldered, very inconspicuously horizontally striate at base but strongly papillose distally, dorsal lamellae low. Endostome with basal membrane constituting less than 1/4 of total length. Segments smooth, about as long as exostome, broadly perforated along center line but almost not keeled. Cilia 1–2, nodulose. Calyptra cucullate, mostly shed before capsule maturity. Spores to 18 µm, finely papillose.