31. Trematodon Michx. 长蒴藓属 chang-shuo xian shu
Fl. Bor. Amer. 2: 289. 1803.
Plants small, light green to yellowish green, gregarious or in loose tufts. Stems erect, simple or rarely branched; central strand present. Leaves usually contorted when dry, oblong to oblong-ovate at the base, gradually to abruptly narrowed from the clasping base to a long awn or linear-subulate acumen; margins entire, usually recurved in the upper part; costa strong, subpercurrent to long-excurrent; upper cells small and somewhat obscure, subquadrate to short-rectangular; lower cells at the clasping base, elongate, thin-walled, smooth; alar cells not differentiated. Autoicous. Perichaetial leaves clearly larger than the vegetative ones. Setae elongate, straight, yellowish to yellowish brown; capsules suberect, usually curved above, cylindric, the neck slender, as long as or longer than the urns, usually strumose at the base; opercula obliquely long-rostrate; annuli simple or compound; peristome absent or present, with 16 linear-lanceolate teeth, usually undivided, perforate or forked, vertically striate on outer surface. Calyptrae cucullate, smooth. Spores 20–30 µm in diameter, subreniform, distinctly papillose.