4. Thamnobryum Nieuwl. 木藓属 mu xian shu
Amer. Midl. Naturalist 5: 50. 1917. Thamnium Schimp., Bryol. Eur. 5: 211. 1852, hom. illeg.
Plants rigid, medium-sized to rather large or robust, yellowish green, scarcely to somewhat glossy, often in loose tufts. Primary stems creeping; secondary stems suberect to dendroid, 1–2-pinnately branched, often with complanate branches; central strand scarcely differentiated; pseudoparaphyllia few, foliose. Stipe leaves remotely spaced, broadly ovate-lanceolate or triangular-lanceolate, acute or shortly acuminate at the apex. Stem leaves ovate to ovate-oblong or ovate-lingulate, usually concave; branch leaves similar, but smaller; margins serrate above; costae single, thick, vanishing under leaf apex, smooth or often with spines at the back; apical leaf cells rounded-quadrate; median cells hexagonal, rhombic to rhomboidal, usually thick-walled, not porose, rarely thin-walled; basal juxtacostal cells narrowly rectangular; alar cells scarcely differentiated. Dioicous or autoicous. Perichaetia on secondary stems. Inner perichaetial leaves shortly ovate-lanceolate or oblong-lanceolate. Setae elongate, smooth; capsules oblong-ovoid to shortly cylindrical, with a short apophysis; opercula obliquely long-rostrate; annuli well differentiated, inflated; peristome double; exostome teeth lanceolate, cross-striolate at the base, finely papillose above; endostome segments linear-lanceolate, as long as the teeth, keeled, perforate; basal membrane high; cilia well developed. Calyptrae cucullate, smooth. Spores spherical, finely papillose.