10. Rhytidium (Sull.) Kindb. 垂枝藓属 chui zhi xian shu
Bih. Kongl. Svenska Vetensk.-Akad. Handl. 6(19): 8. 1882. Hypnum sect. Rhytidium Sull. in A. Gray, Manual (ed. 2) 674. 1856.
Plants mostly large or robust, 5–13 cm long, stiff, green, yellowish to brownish green or yellowish brown, in loose and dense wefts. Stems round; main stems erect or erect-spreading, often with brown rhizoids at ventral or dorsal sides; secondary stems erect-spreading, usually irregularly pinnately branched, slightly curved at terminals; in stem cross section a central strand present, with small, thin-walled cells, an inner parenchyma of larger, thin-walled cells, and a sterome of small, thick-walled cells, the epidermis not differentiated from sterome; pseudoparaphyllia loosely located on stems, small, foliose, narrowly triangular, sometimes irregularly toothed. Leaves densely and spirally arranged; stem leaves elongated ovate-lanceolate, slightly concave, rugose and plicate, usually falcate-secund, acuminate at apex; margins often dentate, sometimes slightly decurrent at base; costae single, often slender and long, more than 1/2 the leaf length; laminal cells linear or vermiform, thick-walled, upper leaf cells clearly prorate on dorsal and ventral surfaces; juxtacostal cells rectangular, thick-walled, often pitted; alar cells clearly differentiated, small, quadrate or irregular, often yellowish, usually extending along margins. Dioicous. Perichaetia and perigonia similar, bud-like, laterally on stems, often with hairy paraphyses; perigonia sometimes on tips of short branchlets. Inner perichaetial leaves narrowly ovate-lanceolate, toothed above, long-acuminate at apex; ecostate. Setae slender, elongate, reddish brown, smooth, often twisted when dry; capsules oblong-ovoid, erect or curved; annuli usually differentiated; opercula highly conic, shortly obliquely rostrate; peristome double; exostome teeth 16, narrowly lanceolate, orange yellow, outer surface cross-striate, with hyaline-bordered margins, keeled, finely papillose above, fusing at base, densely trabeculate on inner surface; endostome segments narrowly elongated, light yellow, nearly smooth, perforated along median line; basal membrane high; cilia usually 2, linear or nodulose. Calyptrae cucullate, smooth or with few hairs. Spores spherical, small, yellow, finely papillose.