1. Tortella fragilis (Hook. & Wils.) Limpr. 折叶纽藓 zhe-ye niu xian
Laubm. Deutschl. 1: 606. 1888. Mollia fragilis (Hook. & Wils.) Lindb., Musci Scand. 21. 1879. Didymodon fragilis Hook. & Wils. in Drumm., Musci Amer., Brit. N. Amer. 127. 1828. Type. North America.
Trichostomum lonchobasis C. Müll., Nuovo Giorn. Bot. Ital., n. ser. 3: 102. 1896. Type. China: Shaanxi (Schen-si), Kuan-tou-san, July 1894, P. J. Giraldi 926 (isotype H).
Plants medium-sized to large, (1–)2–4(–6) cm high, yellowish green to brown green, in dense tufts. Stems erect, usually simple, radiculose at base. Leaves appressed to erect-curved when dry, erect-spreading when moist, linear-lanceolate or oblong-lanceolate, 5.0–7.5 mm long, often fragil eat tips, somewhat sheathing at base; margins plane or somewhat undulate or narrowly incurved; costa shortly excurrent, ending in an awn; upper leaf cells quadrate to hexagonal, 5–8 µm in diameter, usually bistratose, pluripapillose, with simple papillae, relatively thin-walled; basal cells sharply differentiated, rectangular, smooth, forming a V-shaped base. Sporophytes not seen.