1. Tetraphis Hedw. 四齿藓属 si-chi xian shu
Sp. Musc. Frond. 45. 1801. Georgia sect. Tetraphis (Hedw.) Braith., Brit. Moss Fl. 1: 28. 1880.
Plants small, bright green to reddish brown, in dense tufts. Stems erect, slender; triangular in cross section; central strand present. Leaves sparse, arranged in 3 ranks, lower leaves broadly ovate, acute at apex; upper leaves oblong-ovate, acuminate at apex; margins entire; costa strong, ending near leaf apex; upper and median leaf cells rounded-hexagonal, rather thick-walled; lower cells elongate, irregularly rectangular. Protonemata filamentous, short-lived. Gemmae cups often present at the tips of sterile plants. Autoicous (with perigonia and perichaetia terminal on different branches or sometimes some stems producing only perigonia). Perichaetial leaves lanceolate. Setae elongate; capsules narrowly cylindrical, erect, symmetric or slightly curved; opercula conic; annuli none; peristome 4, triangular, deeply inserted below the mouth, yellowish brown. Calyptrae long-conic, plicate. Spores spherical, smooth to slightly roughened.