3. Plagiobryum japonicum Nog. 日本平蒴藓 ri ben ping shuo xian
J. Jap. Bot. 27: 122. f. 50. 1952. Type: Japan. Honsyu, Mt. Yatugatake, Yano 339.
Plants medium-sized to rather large, 20–30 mm high or higher, dark reddish brown or sometimes green, in tufts. Stems branched by numerous innovations above, distantly foliate below, with rhizoids throughout. Leaves ovate, oblong-ovate to obovate, appressed when dry, imbricate when moist, 1.0–2.2 mm × 0.8–1.1 mm, acute or apiculate at apex, cucullate above, distinctly decurrent at base; margins entire, borders not differentiated; costae ending below apex; median leaf cells rhombic to elongate-hexagonal, 40–78 µm × 16–27 µm, thin-walled; upper cells broader; basal cells rectangular. Setae ca. 10 mm long; capsules horizontal to pendulous, oblong-pyriform or club-shaped, ca. 4.5 mm long, neck as long as the urn; mouth oblique; opercula conic; peristome double; exostome teeth short, obtuse, smooth or nearly so; endostome segments longer than teeth, linear, smooth. Spores ca. 35 µm in diameter, coarsely papillose.