四齿藓科 si-chi xian ke
by Li Xing-jiang, Si He, and Zhang Da-cheng
Plants minute to small, slender, bright green, dark green or reddish brown, not glossy, gregarious or in dense tufts. Protonemata filamentous, ephemeral or leaf-like (flaps) and persistent, forming large patches mixed with stems. Stems erect, usually simple, rarely branched. Leaves sparse, erect-spreading, usually arranged in 3–5 ranks, broadly ovate to ovate-lanceolate or oblong-lanceolate, acute to acuminate at apex; margins entire or bluntly denticulate, not bordered; costa single, reaching above the middle or ending below the apex, sometimes weak or rarely lacking; leaf cells unistratose, smooth, upper and median cells green, rounded-hexagonal or irregularly rhombic to oblong-rhomboidal; lower cells elongate. Autoicous. Perigonia rosulate with numerous paraphyses. Perichaetia budlike, without paraphyses; perichaetial leaves larger than stem leaves. Setae elongate, slender, erect; capsules cylindrical or ovoid-cylindrical, erect, symmetric or nearly so, smooth; opercula conic; annuli absent; peristome nematodontous, consisting of whole cells, four in number, narrowly triangular, inserted below the mouth; columella disconnected to opercula. Calyptrae long-mitrate, usually plicate, naked, deeply lobed at base. Spores spherical, smooth to finely roughened.