31. Tortella (Lindb.) Limpr. in Rab. 纽藓属 niu xian shu
Laubm. Deutschl. 1: 520. 1888. Mollia Lindb. sect. Tortella (Lindb.) Braithw. Brit. Moss Fl. 1: 230: 247. 1885. Mollia subgen. Tortella Lindb., Musci Scand. 21. 1879.
Plants small to medium-sized, sometimes rather large, to 6 cm high, green to dark green or reddish brown, in loose or dense tufts. Stems erect, simple or branched; central strand absent or weak to strong. Leaves often crowded, appressed or contorted-curved to strongly crisped when dry, spreading or reflexed when moist, ligulate to oblong or linear-lanceolate or oblong-lanceolate, often channeled above, narrowly to broadly acute, somewhat sheathing at base; margins plane or somewhat undulate or narrowly incurved, entire to weakly serrulate or crenulate with projecting papillae; costa subpercurrent to percurrent or excurrent as a short awn; in cross section 2 stereid bands present; upper leaf cells quadrate to hexagonal, green, often unistratose, sometimes bistratose, pluripapillose, with either branched or simple papillae; basal cells often sharply differentiated, rectangular, smooth, forming a V-shaped base. Dioicous or autoicous. Setae slender, yellowish to reddish brown; capsules erect or slightly inclined, oblong-ovoid to cylindric; peristome teeth 32, linear to filiform, often twisted counterclockwise, densely papillose; basal membrane low or absent; annuli differentiated, of 1–4 rows of vesiculose cells; opercula long conic-rostrate. Calyptrae cucullate, smooth. Spores spherical, yellowish brown, smooth or papillose.