11. Hypnum oldhamii (Mitt.) A. Jaeger 南亚灰藓 nan ya hui xian
Ber. Thätigk. St. Gallischen Naturwiss. Ges. 1877–78: 331 (Gen. Sp. Musc. 2: 395). 1880. Stereodon oldhamii Mitt., J. Proc. Linn. Soc., Bot. 8: 154. 1864. Type: Japan.
Stereodon circinatulus (Schimp. ex Besch.) Broth., Bull. Herb. Boissier, ser. 2, 2: 990. 1902. Hypnum circinatulum Schimp. ex Besch., Ann. Sci. Nat., Bot., ser. 7, 17: 389. 1893.
Plants medium-sized, up to 8 cm long, yellowish green or brownish green. Stems prostrate, regularly pinnately branched, branches short, flattened, 4–7 mm long; in stem cross section epidermal cells not inflated, outer cortical cells 4 layers, thick-walled, yellowish brown, medullar cells enlarged, hyaline, usually thick-walled, central strand slightly or not developed; pseudoparaphyllia few, lanceolate or rounded foliose, sometimes dentate. Stem leaves falcate-secund toward one side or circinate, ovate-lanceolate or triangular-lanceolate, 1.6–2.5 mm × 0.45–0.70 mm, slenderly acuminate; margins plane, serrulate near the apex; costae double, short, sometimes indistinct; median leaf cells linear, thick-walled, basal cells colored or hyaline; alar cells excavate, consisting of a few large, hyaline cells and some quadrate cells above the inflated cells; branch leaves narrower, slenderly acuminate, circinate, 1.3–1.8 mm × 0.30–0.45 mm; median leaf cells 50–80 µm × 3 µm, thick-walled; alar cells not clearly differentiated, usually with a large hyaline cell, but not excavate. Dioicous. Perichaetial leaves lanceolate, slenderly acuminate, serrulate near the apex, plicate. Setae reddish brown, twisted when dry, 1.5–3.0 cm long; capsules reddish brown or dark brown, more or less cylindrical, 1.5–2.0 mm long, erect or arcuate below the mouth, smooth, not constricted below the mouth when dry; opercula shortly rostrate; annuli developed with 2 rows of cells; peristome typically hypnoid, with 1–2 cilia. Calyptrae not seen. Spores roughened, 18–25 µm in diameter.