18. Racomitrium microcarpum (Hedw.) Brid. 小蒴砂藓 xiao-shuo sha xian
Muscol. Recent. Suppl. 4: 79. 1819[1818]. Racomitrium heterostichum var. microcarpum (Hedw.) Boul., Musc. France 1: 360. 1884. Racomitrium heterostichum subsp. microcarpum (Hedw.) Loesk., Laubm. Eur. 187. 1913. Trichostomum microcarpum Hedw., Sp. Musc. Frond. 112. 1801. Type. Europe.
Racomitrium heterostichum var. ramulosum (Lindb.) Corb., Mém. Soc. Sci. Nat. Cherbourg 26: 260. 1889. Racomitrium heterostichum subsp. ramulosum (Lindb.) Dix., Stud. Handb. Brit. Mosses (ed. 2), 167. 1904. Racomitrium ramulosum Lindb., Acta Soc. Sci. Fenn. 10: 550. 1875.
Plants medium-sized, 2–4 cm long, yellowish green or green above, brown and blackish brown below, sometimes appearing grayish due to hyaline hair-points, in large, dense cushions. Stems subpinnately branched, with long or short branches; central strand absent. Leaves imbricately appressed when dry, erect-spreading when moist, ovate-lanceolate, usually secund, somewhat keeled above, with long, flexuous, hyaline and dentate hair-points; margins recurved on one side up to the leaf apex, other side to 3/4 the leaf length, unistratose in cross section; costa strong, percurrent, clearly convex on the dorsal side; leaf cells unistratose, strongly sinuosely thick-walled, sometimes with papillose walls; upper and median cells rectangular, 24–30 µm × 8–10 µm; basal cells linear, 25–50 µm × ca. 9 µm; alar cells not differentiated, with only a row of 10–20 hyaline marginal cells, thin-walled. Perichaetial leaves rounded-ovate, without or with short hyaline hair-points. Setae elongate, erect, 5–8 mm long; capsules oblong-ovoid, 1.5–2.0 mm long; opercula long-rostrate; peristome teeth linear-lanceolate, divided to the base, densely papillose. Calyptrae mitrate. Spores spherical, 12–14 µm in diameter.