8. Helodium Warnst. 沼羽藓属 zhao-yu xian shu
Krypt.-Fl. Brandenburg, Laubm. 2: 675, 692. 1905, nom. cons.
Thuidium sect. Elodium (Sull.) Braithw., Brit. Moss. Fl. 3: 8. 1896. Hypnum subg. Elodium (Sull.) Lesq. & Jam., Man. N. Amer. Moss. 329. 1884. Thuidium subg. Elodium (Sull.) Lindb., Musc. Scand. 31. 1879. Elodium (Sull.) Aust., Musci Appalach. 52. 1870. Hypnum sect. Elodium Sull. in Gray, Manual (ed. 2), 668. 1856.
Plants rather robust, green or yellowish green, rarely brownish, not shinning or slightly shinning, in tufts or cushions. Stems erect or ascending, simple or forkedly branched, but usually regularly pinnately branched; paraphyllia dense, filamentous, simple or branched, pale, brownish when old; central strand absent. Stem leaves and branch leaves similar, gradually narrowed from an ovate-lanceolate or cordate base to a lanceolate apex, longitudinally plicate, restricted at base; margins entire or serrate, revolute above, long ciliate or smooth at base; costa rather rigid, reaching upper portion of leaf apex; leaf cells hyaline, elongate-hexagonal or oval-hexagonal, basal cells rectangular. Autoicous or dioicous. Inner perichaetial leaves erect, lanceolate, deeply plicate, pale; costa ending below leaf apex. Setae slender, smooth; capsules ovoid or cylindrical, strongly recurved or horizontal, brownish; annuli present, stomata present at hypophysis; opercula conic; exostome teeth yellowish brown; cilia weak, usually 3. Calyptrae smooth. Spores not seen.