1. Tortella fragilis (Hook. & Wils.) Limpr., Laubm. Deutschl. 1:606. 1888; Didymodon fragilis Hook. & Wils. in Drumm., Musci Amer., Brit. N. Amer. 127. 1828.
折叶纽藓
Mollia fragilis (Hook. & Wils.) Lindb., Musci Scand. 21. 1879.
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.
Type. North America.
Chinese specimens examined: FUJIAN: Wuyi Shan (Mt.), P.-C. Chen 729 (PE). GANSU: G.H. Potanin s.n. (H). GUANGXI: Rong-an Co., R.-G. Lung 208 (HKAS). GUIZHOU: Fan-jing Shan (Mt.), B.-G. Zhong 188 (PE). HENAN: Xi-xia Co., J.-X. Luo 288 (PE). HUBEI: Sheng-nong-jia (Mt.), K.-Y. Guan 802551 (HKAS). HUNAN: Sang-zhi Co., D.-K. Li 18323 (HKAS, SHM). NEI MONGOL: He-lan Shan (Mt.), Z.-G. Tong 1305 (MO, PE). QINGHAI: Nang-qin Co., B.-C. Tan 95-162 (FH, MO). SHAANXI: Hu Co., M. Wang 297 (HKAS); Qing-ling (Mt.), P.-C. Chen 553 (MO, PE); western Tai-bai Shan (Mt.), Z.-P. Wei 6386 (HKAS, WUG). SICHUAN: Ba-tang Co., S. He 31700 (MO); Mi-yi Co., K.-K. Chen 279 (HKAS); Nan-ping Co., S. He 30138 (MO); Ruo-er-gai Co., S. He 30699 (MO); Song-pan Co., S. He 30406 (MO); Tian-quan Co., S. He 32030 (MO); Ya-jiang Co., S. He 31930b (MO). XINJIANG: Bu-ge-da (Mt.), A.-R. Li 5682 (PE); He-jing Co., S. He 951158 (MO); Ku-che Co., S. He 951209 (MO); Tian Shan (Mt.), R.-C. Qin 3497 (PE); Urumqi Co., S. He 951079 (MO). XIZANG: Ba-qing Co., K.-Y. Zhao 53a (HKAS); Chang-du City, M. Zang 5297 (HKAS); Ya-dong Co., M. Zang 811 (HKAS). YUNNAN: Bin-chuan Co., M.-K. Cui 772b (HKAS); Li-jiang Co., X.-J. Li 85340 (HKAS).
Habitat: on rocks, soil, or rotten wood in forest or alpine regions; Distribution: China, Japan, Russia, Europe, and North America.
Illustration: C. Gao (ed.) 1996 (Pl. 52, figs. 8–11).
