5. Hypnum densirameum Ando 密枝灰藓 mi zhi hui xian
J. Sci. Hiroshima Univ., Ser. B, Div. 2, Bot. 8: 13. 1957. Type: Japan. Honshu, Pref. Hiroshima, Ando 21224.
Plants soft, slender, brownish green, in dense mats. Stems prostrate, up to 10 cm long, radiculose; in stem cross section epidermal cells not hyaline and inflated, outer cortical cells 4–6 layers, dark brown, medullar cells large, hyaline, central strand well developed; densely pinnately branched, flattened, branches 3–5 cm long; pseudoparaphyllia lanceolate. Stem leaves falcate-secund, triangular-lanceolate to oblong ovate-lanceolate, 1.6–2.0 mm × 0.55–0.72 mm, slenderly acuminate at apex; margins recurved near the leaf bases, entire, except serrulate near the apex; costae double, distinct; median leaf cells very linear, 50–70 µm × 2–3 µm, thick-walled; basal cells thick-walled, brownish, porose; alar cells lax, hyaline, small, subquadrate, with 3–5 rows of cells at margins; branch leaves smaller, 1.3–1.7 mm × 0.3–0.4 mm, narrowly lanceolate, falcate-secund or circinate, alar cells distinctly differentiated. Autoicous. Inner perichaetial leaves lanceolate, plicate, slenderly acuminate ending with a filiform, serrulate apex; costae double, distinct. Setae 3.5–4.0 cm long, smooth, pale brownish, twisted when dry; capsules horizontal, ellipsoidal, arcuate, 1.5–2.0 mm long, pale green to pale brown, wrinkled when dry; opercula conic, bluntly apiculate, mammillose-rostrate; annuli developed, in 2–3 rows; peristome typically hypnoid, with 2–3 cilia. Calyptrae not seen. Spores 14–17 µm in diameter, very minutely roughened.