2. Helicodontium formosicum (Card.) Buck 台湾旋齿藓 tai-wan xuan-chi xian
J. Hattori Bot. Lab. 47: 52. 1980. Schwetschkea formosica Card., Beih. Bot. Centralbl. 19(2): 125. 1905. Type. China: Taiwan, Mt. Maruyama, Faurie 6 (isotype H).
Fabronia formosana Sak., Bot. Mag. (Tokyo) 46: 378. 1932. Type. China: Taiwan, Tai-chiu, Noko-gun, Horisha, Sasaoka 2101.
Plants delicate, green or yellowish green, in dense patches. Stems slenderly weak, prostrate, 3–4 cm long, irregularly branched, erecto-patent or creeping, ascending above. Leaves small, erect or erect spreading, not appressed, widely lanceolate, acute, 0.5–0.8 mm × 0.16–0.25 mm; leaf margins plane, mostly entire below, serrulate above; costa slender, weak, disappearing in the middle of leaf; median and upper leaf cells elliptic or narrowly rhomboidal, thin-walled; alar cells quadrate or flat quadrate, in several rows, thin-walled. Monoicous or autoicous. Perichaetial leaves small, ovate-lanceolate, gradually tapering to a narrow apex. Setae slender, 5–6 mm long, yellowish green, smooth, twisted above when dry; capsules ovoid to cylindrical, erect or patent, 0.8–0.9 mm long, 0.4–0.5 mm in diameter; opercula shortly rostrate; peristome double; exostome teeth triangular at base; endostome segments linear, smooth, as long as exostome teeth; basal membrane low. Spores 20–25 µm in diameter, smooth.