8. Ptychomitrium tortula (Harv.) Jaeg., Ber. Thätigk. St. Gallischen Naturwiss. Ges. 1872–73:105. 1874; Didymodon tortula Harv. in Hook., Icon Pl. Rar. 1: 18. 1836.
Glyphomitrium tortula (Harv.) Mitt., J. Proc. Linn. Soc. (London), Suppl. Bot. 1: 46. 1859.
Ptychomitrium mairei (Thér.) Broth., Symb. Sin. 4: 4. 1929. Brachysteleum mairei Thér., Bull. Soc. Sci. Nancy sér. 4, 3: 4. 1925. Type. “Colline de Ma-li-ouan, 2500 meters.” (isotype H).
Ptychomitrium speciosum Wils., Kew J. Bot. 9: 325. 1857, nom. nud.
Plants large, rather robust, (6–)9–15 cm high, green to reddish brown, in loose tufts. Stems branched; central strand well developed. Leaves 5.5–7.0 mm long, strongly crisped and contorted, somewhat shining when dry, erect-spreading to wide-spreading when moist, gradually narrowed from a broadly oblong, distinctly plicate base to lanceolate or linear-lanceolate acumen, strongly keeled and somewhat secund above; margins recurved below, irregularly toothed above, each tooth consisting of several cells; costa single, strong, becoming narrow above, subpercurrent or ending just below the apex; upper leaf cells irregularly quadrate, 6–8 µm wide, with slightly thickened walls; median cells short-rectangular to rectangular, 8–11 µm x 5–6 µm, strongly sinuose; basal cells elongate, 18–39 µm x 3–4 µm, with strongly sinuose walls. Autoicous. Perichaetial leaves similar to the upper stem leaves, but slightly larger. Setae straight, yellow or reddish brown, 5–7 mm long, twisted above; capsules often 2–4 per perichaetium, erect, oblong-ellipsoid, yellowish brown, ca. 1.5 mm long; annuli undifferentiated; peristome teeth elongate, linear, yellowish brown, forked in the upper part, sometimes perforated in the middle, densely and finely papillose; opercula with a long beak. Calyptrae mitrate, reaching the middle of capsule, longitudinally plicate, lobed at the base. Spores spherical, nearly smooth.
Type. Nepal: Wallich s.n.
Chinese specimens examined: SICHUAN: Ma-er-kang Co., X.-J. Li 1031 (HKAS); Yen-yuan Co., Handel-Mazzetti 4058 (MO). XIZANG: Cha-yu Co., M.-Z. Wang 12599a (PE); Ya-dong Co., M. Zang 485 (HKAS). YUNNAN: Bao-shan, J.-H. Peng 21 (PE); Da-li Co., Redfearn et al. 1558 (MO, NY, SMS); Fu-gong Co., M.-Z. Wang 6738a (PE); Li-jiang Co., Q.-W. Wang 3801 (PE); Yu-long Shan (Mt.), Handel-Mazzetti 4295 (as P. tortula var. brevipes, H, MO, NY); Yang-bi Co., Redfearn et al. 392 (MO, NY, SMS).
Habitat: on rocks or terrestrial in mountains; Distribution: China, Nepal, Sikkim, and Bhutan.
The distinctive characters of Ptychomitrium tortula are: 1) plants rather robust, normally 6–10(–15) cm high; 2) leaves strongly crisped and contorted when dry, keeled and concave with irregular teeth above; and 3) median and basal leaf cell walls strongly sinuose, somewhat similar to the leaf cells seen in Racomitrium. This character suggests relationship between Ptychomitrium and Racomitrium.
Some robust plants of Ptychomitrium gardneri, which is the most common species in southwestern China, resemble those of P. tortula. However, P. gardneri is easily distinguished from the latter by having much more branched plants, crisped, but not strongly contorted leaves, and basal leaf cells with thin, straight walls.
Illustrations: Pl. 144, figs. 1–11.