Dicranum japonicum Mitten 1891

Dicranum japonicum has a wide distribution range in China. It shows considerable variation in plant habit and size. Type specimens of Dicranum longicylindricum, D. schensianum, D. japonicum var. yunnanense exhibit identical morphological concept we understand in China for D. japonicum.

Plants coarse, fairly robust, up to 5(–13) cm high, yellowish green or brownish green, shiny or not, in loose tufts. Stems erect, simple or rarely branched, loosely foliate, densely tomentose throughout. Leaves flexuose or somewhat falcate-secund when dry, erect-patent when moist, lanceolate, 7–11 mm long, gradually narrowed from an oblong base to a long subulate or keeled, sometimes undulate, acumen; margins plane, sharply serrate in the upper 1/3; costa narrow, slender, shortly excurrent, ending in a short hairpoint, with 2–3 serrate lamellae at back in the upper part; upper cells oblong-rhomboidal, ca. 60 µm × 9 µm, thick-walled, slightly porose; basal cells elongate, rounded rectangular, ca. 100 µm × 10 µm, thick-walled, porose; alar cells broadly rectangular, inflated, ca. 50 µm × 20 µm, thin-walled, bistratose, brownish. Dioicous. Male plants dwarfed, 1–3 mm high. Perichaetial leaves ca. 7–10 mm long, high convolute-sheathing at base, abruptly narrowed to a long, subulate, serrulate apex. Setae single, twisted when dry, 3–6 cm long, yellowish or reddish brown; capsules cylindric, curved, inclined to horizontal, urns 3.0–4.5 mm × 0.8–1.0 mm; stomata present at neck; opercula long-rostrate, about as long as the urns; peristome teeth lanceolate, ca. 0.75 mm long, 2–3 divided to the middle, densely papillose above, vertically pitted-striolate below. Calyptrae ca. 8 mm long. Spores ca. 20 µm in diameter, yellowish, coarsely papillose.

Distribution: China, Korea, Japan, and Russian Far East.

Habitat: on humic soil, rocks, or rotten logs.

Dicranum japonicum var. yunnanense Salm., J. Linn. Soc., Bot. 34: 452. 1900. syn. nov. Type. China: Yunnan, Mupeh Kuei, A. Henry 6165 (holotype BM). Dicranum longicylindricum C. Gao & T. Cao, Bryobrothera 1: 218. 1992. syn. nov. Dicranum cylindricum Broth. in Handel-Mazzetti, Symb. Sin. 4: 27. 1929. Type. China: Yunnan, between Mekong and Salwin, Handel-Mazzetti 1914 (holotype H). Dicranum schensianum C. Müll., Nuovo Giorn. Bot. Ital. n.s. 4: 249. 1897. syn. nov. Type. China: Shaanxi (Schen-si), Schan-kio, G. Giraldi 1436 (holotype B, probably destroyed; isotype H).

Dicranum japonicum là một loài Rêu trong họ Dicranaceae. Loài này được Mitt. mô tả khoa học đầu tiên năm 1891.

日本曲尾藓（学名：Dicranum japonicum）为曲尾藓科曲尾藓属下的一个种。