5. Ptychomitrium linearifolium Reim. in Reim. & Sak., Bot. Jahrb. 64:539. 1931.
Plants medium-sized, to 2–3 cm high, green to yellowish green above, brown to dark brown below, in loose tufts. Stems simple or sparsely branched; central strand well developed. Leaves 3.9–4.6 mm long, crisped or somewhat contorted when dry, erect-spreading to wide-spreading when moist, tapered from an ovate, more or less sheathing base to a long-linear and keeled upper acumen, acute at the apex; margins slightly recurved below, with large, remote teeth above, each tooth consisting of several cells; upper leaf cells obscure, rounded quadrate to subquadrate, 8–10 µm wide, with slightly thickened walls; basal cells elongate, 26–40 µm x 8–13 µm, hyaline, thin-walled. Autoicous. Perichaetial leaves similar to the upper stem leaves. Setae straight, yellow, 4–5 mm long; capsules erect, ellipsoid to oblong-ellipsoid, yellowish brown, 1.5–2.0 mm long; annuli undifferentiated; peristome teeth reddish brown, linear-lanceolate, bifid nearly to the base, sometimes perforate, finely papillose; opercula with a long, erect beak. Calyptrae mitrate, reaching the middle of the capsule, longitudinally plicate, lobed at the base. Spores spherical, finely papillose to nearly smooth.
Type. Japan: Mar. 1879. F. Schaal s.n.
Chinese specimens examined: ANHUI: Huang Shan (Mt.), P.-C. Chen 7323 (PE); Yun-gu Temple, 17 May 1982, C. Gao s.n. (MO). FUJIAN: Wuyi Shan (Mt.), D.-K. Li & C.-H. Gao 11833 (SHM). HUNAN: Liu-yang Co., C. Gao & G.-C. Zhang 325 (IFSBH). JIANGXI: Mt. Lu, C. Gao 40836 (IFSBH). SICHUAN: Bi Shan (Mt.), P.-C. Chen 1076 (PE); Nan-ping Co., S. He 30205 (MO). ZHEJIANG: De-qing Co., P.-C. Wu 1210 (MO); Lin-an Co., P.-C. Wu 8091 (MO); Mt. Jiu-long, R.-L. Hong & Z.-L. Liu 163 (HSNU); Mt. Tian-mu, S.-R. Feng s.n. (PE); Tian-tai, D.-K. Li 6533 (SHM).
Habitat: on rocks and boulders, sometimes on thin soil over rocks in mountains; Distribution: China, Korea, and Japan.
Ptychomitrium linearifolium is characterized by having leaves that are crisped when dry, tapered from an ovate base to long-linear toothed upper acumen. Sometimes, specimens of Ptychomitrium gardneri with long upper linear acumen can be misidentified as P. linearifolium. However, the former species differs by having more robust, multi-branched plants, and strongly plicate leaf bases.
Illustrations: Pl. 142, figs. 1–10.