扭叶藓科 niu ye xian ke
by Wu Peng-cheng
Plants often elongate, very slender, soft or rigid, green, light yellow to brownish green, or sometimes blackish, not glossy. Primary stems creeping, often covered with scale-like leaves, with dense reddish brown rhizoids at the base; secondary stems ascending or pendulous, rarely dendroid, to ca. 10 cm long or longer, loosely to irregularly or densely, regularly pinnately branched, often terete, rarely complanate, sometimes with flagelliform branches; a central strand present or absent; pseudoparaphyllia absent. Leaves appressed when dry, usually erect-spreading, sometimes reflexed above when moist, ovate, ovate-lanceolate, lanceolate, or broadly ovate, plicate or undulate, rarely auriculate at the base, acuminate above, often slenderly tapering or twisted at the apex; branch leaves smaller, sometimes dimorphic; margins serrulate or dentate; costae single, slender, vanishing above the mid-leaf; leaf cells hexagonal, oblong-oval, rhomboidal to nearly linear, unipapillose or pluripapillose, or with dense, minute papillae along cell walls, rarely smooth, thin-walled or thick-walled, or sometimes distinctly porose; marginal cells indistinctly or clearly differentiated; alar cells differentiated or scarcely differentiated. Dioicous. Setae short to elongate, smooth, rarely mammillose; capsules ovoid or subglobose or cylindrical; opercula conic, obliquely rostrate; annuli absent or scarcely differentiated; peristome double; exostome teeth lanceolate, papillose; endostome segments narrowly lanceolate to linear-lanceolate, as long as or shorter than the teeth, or reduced, smooth or papillose; basal membrane low or high, smooth or finely papillose; cilia developed or rudimentary. Calyptrae cucullate, smooth or hairy. Spores spherical, minutely papillose.