28. Brachythecium populeum (Hedw.) Schimp. in B.S.G. 长肋青藓 chang le qing xian
Bryol. Eur. 6: 7. pl. 535. 1853. Cirriphyllum populeum (Hedw.) Loeske & M. Fleisch., Allg. Bot. Z. Syst. 13: 22. 1907. Hypnum populeum Hedw., Sp. Musc. Frond. 270. 1801. Type: Sweden.
Brachythecium populeum var. quelpaertense (Cardot) Takaki, J. Hattori Bot. Lab. 15: 65. 1955. Brachythecium quelpaertense Cardot, Bull. Soc. Bot. Genève, ser. 2, 3: 293. 1911.
Brachythecium populeum var. yamamotoi (Sakurai) Takaki, J. Hattori Bot. Lab. 15: 68. 1955. Brachythecium yamamotoi Sakurai, Bot. Mag. (Tokyo) 50: 371. 1936.
Plants rather elongate, dark green, somewhat glossy, in loose mats. Stems prostrate, often uni-pinnately branched, with ascending, simple branches, julaceous when dry, attenuate at tips. Stem leaves triangularly ovate, 1.4–1.6 mm × 0.59–0.86 mm, plane or somewhat concave, slightly plicate, shortly acuminate at apex, truncate at insertion; margins plane, entire below, serrulate above; costae strong, percurrent; median leaf cells elongate-rhomboidal, 36–55 µm × 6–7 µm; alar cells numerous, quadrate or shortly rectangular, somewhat thick-walled, extending close to costa at leaf base; branch leaves narrowly ovate-lanceolate, widest near base, somewhat cordate or nearly truncate at insertion. Autoicous. Perichaetial leaves lanceolate, weakly costate. Setae ca. 10–15 mm long, reddish brown, papillose above, smooth below; capsules elongate-ellipsoidal, reddish brown; opercula shortly conic-rostrate; exostome teeth ca. 450 µm long; endostome segments as long as exostome teeth; cilia long, in groups of 2–3. Spores 12–15 µm in diameter, finely papillose.