2. Ceratodon Brid., Bryol. Univ. 1: 480. 1826.
Plants small to medium-sized, green to yellowish green, in dense tufts. Stems erect, simple or branched; central strand present. Leaves appressed, contorted when dry, lanceolate or narrowly ovate-lanceolate, gradually acuminate; margins distinctly reflexed or revolute, notched or irregularly serrulate near the apex; costa single, subpercurrent to shortly excurrent; laminal cells quadrate to short-rectangular, thick-walled, smooth, not much differentiated from apex to base. Dioicous. Perichaetial leaves highly convolute-sheathing at base, gradually narrowed into a short, slender acumen. Setae elongate, straight; capsules suberect and nearly symmetric or strongly inclined to horizontal and asymmetric, long-cylindric, deeply furrowed when dry, strumose at base; opercula short conic-rostrate; annuli developed, in 2–3 rows of thick-walled, large cells, revoluble; stomata present; peristome teeth 16, lanceolate, reddish brown within, pale yellowish at the margins, with a low basal membrane, divided nearly to the base, transversally striolate below, papillose above. Calyptrae cucullate, smooth, entire. Spores spherical, yellow, nearly smooth.
The strongly furrowed capsules with strumae at the base, the reddish brown and bifid peristome teeth, the clearly recurved leaf margins, and the subquadrate to quadrate leaf cells distinguish Ceratodon from its closely related genera. There are about 4 to 5 species currently recognized in the world. Two species are known from China. Burley and Pritchard (1990) treated C. stenocarpus as a variety of C. purpureus. However, we consider the two species distinctive in Chinese material.