12. Racomitrium heterostichum (Hedw.) Brid. 异枝砂藓 yi-zhi sha xian
Muscol. Recent. Suppl. 4: 79. 1819. Grimmia heterosticha (Hedw.) C. Müll., Syn. Musc. Frond. 1: 807. 1849. Trichostomum heterostichum Hedw., Sp. Musc. Frond. 109. 1801. Type. Germany.
Plants usually large to robust, up to 8–10 cm long, yellowish green above, dark brownish or blackish brown below, often appearing grayish due to hyaline hair-points, in dense cushions. Stems densely branched with long or short branches; central strand absent. Leaves imbricately appressed when dry, erect-spreading when moist, narrowly ovate-lanceolate, 2.5–3.5 mm long, keeled above, sometimes secund, with long, dentate, hyaline hair-points, the hair-points often decurrent at base; margins recurved on both sides; costa percurrent; upper and median leaf cells quadrate to short-rectangular, 10–20 µm × 8–10 µm, sinuosely thick-walled, smooth, unistratose at margins; basal cells rectangular to elongate-rectangular, 15–35 µm × ca. 10 µm, strongly sinuosely thick-walled; alar cells scarcely differentiated, with only a row of 3–10 slightly larger, rectangular, straight-walled cells. Perichaetial leaves smaller than stem leaves, ovate-lanceolate, narrowly obtuse at apex, with shorter hyaline hair-points. Setae erect, 4–8 mm long; capsules cylindrical, 1.5–3.0 mm long; opercula long-rostrate; peristome teeth linear-lanceolate, divided to the base, densely papillose. Spores spherical, 14–17 µm in diameter.