15. Hypnum revolutum (Mitt.) Lindb. 卷叶灰藓 juan-ye hui xian
Öfvers. Förh. Kongl. Svenska Vetensk.-Akad. 23: 542. 1867 . Stereodon revolutus Mitt., J. Proc. Linn. Soc., Bot., Suppl. 1: 97. 1859. Type: China. Eastern Tibet (Xizang).
Stereodon plicatilis Mitt., J. Proc. Linn. Soc., Bot., 8: 40. 1864.
Plants medium-sized, 3–5 cm long, yellowish green or yellowish brown. Stems creeping, erect or nearly erect, flattened or subjulaceous, 3–7 mm long, pinnately branched; in stem cross section central strand slightly developed, outer epidermal cell walls thin-walled; pseudoparaphyllia foliose or shortly lanceolate. Stem leaves and branch leaves similar, falcate-secund, ovate-lanceolate or oblong-lanceolate, slenderly acuminate toward apex, concave, plicate, (1.1–)1.4–1.6(–1.8) mm × (0.3–)0.5–0.7 mm; margins recurved throughout; costae double, sometimes absent; median and upper leaf cells linear, 30–50 µm × 4–5 µm, thin- to somewhat thick-walled; basal cells wider, thick-walled, porose; alar cells subquadrate, numerous, with a few inflated, hyaline cells at basal margins and 8–15 cells extending along the margins. Dioicous. Inner perichaetial leaves erect, oblong-lanceolate, plicate, shortly acuminate, margins entire, costae indistinct. Setae elongate, 1–2 cm long, yellowish brown or reddish brown, twisted when dry; capsules inclined or horizontal, oblong-ellipsoidal, curved, 2–3 mm long, constricted below the mouth when dry; opercula conic, shortly rostrate; annuli developed, in 2 rows, rarely 3 rows; peristome perfect hypnoid, with 2–3 cilia. Spores 12–15 µm in diameter, almost smooth.