3. Barbula Hedw. 扭口藓属 niu-kou xian shu
Sp. Musc. Frond. 115. 1801, nom. cons.
Plants small, slender to rather robust, green, yellowish green to yellowish brown or reddish brown, in loose or dense tufts, or forming cushions. Stems erect, simple or irregularly branched, often radiculose at base; central strand differentiated. Leaves appressed or contorted when dry, erect-spreading when moist, sometimes squarrose, ovate, ovate-lanceolate to linear-lanceolate, or narrow-ligulate to oblong-triangular, gradually acuminate to abruptly acute or rounded obtuse; margins entire, often recurved in lower 1¤2–2¤3 the leaf length; costa stout, percurrent to shortly excurrent, seldom short-awned, rarely ending below apex, in cross section often with two stereid bands; upper leaf cells small, usually rounded-hexagonal or quadrate to short-rectangular, rather thick-walled, obscure, unipapillose or multi-papillose, sometimes mammillose or occasionally smooth; basal cells usually differentiated, often larger, short-rectangular, smooth, hyaline. Gemmae sometimes developed, axillary on stalks or in leaf axils. Dioicous. Perichaetial leaves similar to stem leaves, but slightly larger and often sheathing at the base. Setae elongate, yellowish to sometimes reddish, smooth; capsules erect, rarely inclined, oblong-ovoid to long-cylindrical, rarely curved; annuli often differentiated; peristome teeth 32, slender, filiform, usually twisted counterclockwise, rarely straight, densely papillose; opercula conic, short- to long-rostrate. Calyptrae cucullate, smooth. Spores small, spherical, usually yellowish green, rarely light reddish brown, smooth or weakly papillose.