16. Racomitrium laetum Besch. & Card. 多枝砂藓 dou-zhi sha xian
Bull. Herb. Boissier, ser. 2, 8: 335. 1908. Syntypes. Japan: Nikko, Faurie 504, 506, 515; Sobosan, Faurie 732; Ichifusa, Faurie 1060; Ubayu, Faurie 2812; Komagatake, Faurie 3471; Tokachiyama, Faurie 3384; Korea: Pomasa, Faurie 238; Quelpaert, Faurie 87, 611, 630, 720.
Racomitrium heterostichum var. diminutum (Card.) Nog., Misc. Bryol. Lichenol. 1(15): 1. 1958. Racomitrium diminutum Card., Bull. Herb. Boissier, ser. 2, 8: 335. 1908.
Racomitrium sakuraii Broth. ex Sak., Bot. Mag. (Tokyo) 51: 137. 1937.
Plants large to rather robust, 6–10 cm long, yellowish green above, brownish green below, in large, loose cushions. Stems sparsely irregularly branched; central strand absent. Leaves imbricately appressed, slightly secund when dry, erect-spreading when moist, narrowly lanceolate, keeled above, 1.5–3.0 mm long, hyaline hair-points long, dentate and decurrent; margins recurved on one side, ca. 1/3–1/2 the leaf length, plane or narrowly and short-recurved on the other side, unistratose at margins; costa strong, percurrent, convex on the dorsal side; leaf cells unistratose throughout, strongly sinuosely thick-walled, upper cells subquadrate to shortly rectangular, 7–17 µm × 10–11 µm; median cells rectangular, 9–28 µm × 7–8 µm; basal cells narrowly rectangular, 23–47 µm × 8 µm; alar cells not differentiated, with a row of 12–20, shortly rectangular, hyaline cells, walls straight. Perichaetial leaves rounded ovate, without hair-points. Setae erect, 3.0–3.5 mm long; capsules ovoid, 1.0–1.4 mm long; opercula long-rostrate; peristome teeth linear-lanceolate, divided to the base, densely papillose. Calyptrae mitrate. Spores spherical, 14–16 µm in diameter.