14. Thuidium Bruch & Schimp. in B. S. G. 羽藓属 yu xian shu
Bryol. Eur. 5: 157. 1852.
Plants medium-sized to robust, green, yellowish green or brownish green, often in loosely interwoven mats. Stems procumbent to climbing, bi- to tripinnately branched; paraphyllia abundant on stems and branches, filamentous or foliose, often papillose; central strand present. Stem leaves and branch leaves differentiated or similar, but different in size; stem leaves ovate or ovate-cordate, usually with slender apex, narrowed at base, decurrent, multiplicate; leaf margins revolute, serrulate above; costa not extending to leaf apex, rarely excurrent; leaf cells isomorphic, mostly hexagonal or rounded to rounded-hexagonal, equally thick-walled, uni- or multipapillose. Primary branch leaves similar to the stem leaves, but smaller; secondary or young branch leaves minute, mostly ovate or oblong-ovate, concave; leaf margins erect; costa weak and short. Autoicous or dioicous. Perichaetial leaves lanceolate or ovate-lanceolate, with slender apices, sometimes leaf margins with long cilia; costa ending at leaf apex or slightly excurrent; leaf cells rectangular, smooth or papillose. Setae slender, smooth or densely papillose above; capsules horizontal or declining, ovoid or cylindrical, slightly curved, brownish, smooth; annuli 2–3 rows, revolute, deciduous; opercula acute to conical, obliquely beaked; stomata present; peristome double; exostome teeth yellowish or yellowish brown; basal membrane high, at least 1/3 the length of endostome segments; cilia 2–4, mostly nodulose, rarely rudimentary or lacking. Calyptrae cucullate or campanulate, smooth, rarely scabrous.