11. Didymodon nigrescens (Mitt.) K. Saito    黑对齿藓 hei dui-chi xian

J. Hattori Bot. Lab. 39: 510. 1975. Barbula nigrescens Mitt., J. Proc. Linn. Soc., Bot. Suppl. 1: 36. 1859. Type. Sikkim: J. D. Hooker 169 (NY).

Andreaea yuennanenis Broth., Symb. Sin. 4: 9. 1929. Type. China: Yunnan, Zhong-dian (Chungtien) Co., Handel-Mazzetti 6952 (holotype H).

Barbula subrivicola P.C. Chen, Hedwigia 80: 213. 35 f. 7–13. 1941. Type. China: Sichuan (Setschwan), Yan-yuan (Yenyuen) Co., Handel-Mazzetti 5538 (holotype H).

Barbula subrivicola var. densifolia P.C. Chen, Hedwigia 80: 215. 1941. Type. China: Sichuan (Setschwan), between Yalung and Tschahung, Handel-Mazzetti 2669 (holotype H).

 

Plants small to medium-sized, 10–20 mm high, dark green to dark reddish brown, in cushions or dense tufts. Stems erect, often branched; central strand absent. Leaves appressed or somewhat involute when dry, erect-spreading when moist, broadly ovate- to shortly ovate-lanceolate, 1.3–1.6 mm × 0.3–0.5 mm, narrowly obtuse to blunt at the apex; margins entire, distinctly revolute; costa stout, dark brown, percurrent or ending just below the apex; upper leaf cells rounded hexagonal, 6–12 µm × 8–12 µm, thick-walled, with blunt large papillae; basal cells rectangular, 12–24 µm × 8–14 µm, thick-walled, smooth or sometimes with single papilla. Dioicous. Perichaetial leaves larger than stem leaves. Setae slender, ca. 7 mm long, dark reddish; capsules erect, blackish red, cylindrical, ca. 2.5 mm long; opercula conic-rostrate with a short beak.