棉藓科 mian xian ke
by Li Deng-ke and Robert R. Ireland
Plants slender to rather robust, green or yellowish green, usually glossy, in loose or dense mats. Stems mostly prostrate, complanate, irregularly branched, sometimes with flagelliform branches; cortical cells large, central strand differentiated or absent; paraphyllia and pseudoparaphyllia absent. Stem and branch leaves similar, broadly ovate, elliptical, or ovate-lanceolate, sometimes concave, obtuse, acute or acuminate at apex; dorsal and ventral leaves mostly symmetric, appressed or erect; lateral leaves often larger, asymmetric; margins entire or serrulate; costae double, forked, unequal, rarely absent; median leaf cells elliptical, rhombic or rhomboidal, all smooth, except in Plagiothecium undulatum (Hedw.) Schimp. with minute, cuticular papillae on abaxial surfaces; alar cells distinctly differentiated, shorter, broader, usually distinctly decurrent, consisting of 1–8 rows of quadrate to rectangular cells. Autoicous or dioicous. Perigonia small, bud-like. Perichaetia on short branches. Inner perichaetial leaves small, erect, acuminate, often sheathing at base. Setae slender, straight or curved, smooth, usually reddish; capsules erect, inclined or horizontal, asymmetric, ovoid, ellipsoidal, or cylindrical; often constricted below the mouth; opercula conic at base, obliquely rostrate; annuli often persistent; peristome double; exostome teeth 16, mostly united at base, lanceolate, cross-striolate below; endostome segments divided, keeled; basal membrane high; cilia developed or absent. Calyptrae cucullate, smooth. Spores spherical, yellowish green, smooth or finely papillose.