Ptychomitrium longisetum Reim & Sak., Bot. Jahrb. 64: 541. 1931. Ptychomitrium polyphylloides (C. Müll.) Par., Ind. Bryol. Suppl. 1058. 1898. Brachysteleum polyphylloides C. Müll., Nuovo Giorn. Bot. Ital., n. ser. 3: 107. 1896. Type. China: Shaanxi (Schen-si), Mt. Si-ku-tziu-san, J. Giraldi s.n., July 1894 (isotype BM). Ptychomitrium robustum Broth., Nat. Pflanzenfam. (ed. 2) 11: 10. 1925, nom. nud.

Plants medium-sized to large, somewhat robust, 3–5 cm high, yellowish green to green above, brown below, in tufts. Stems fasciculate, multi-branched; central strand well developed. Leaves 4.5–5.5 mm long, incurved or slightly crisped when dry, erect-spreading to wide-spreading when moist, lanceolate to linear-lanceolate from an ovate or oblong base to keeled acumen, acute at the apex, somewhat concave and strongly plicate at the base; margins recurved on one or both sides below, with large, remote teeth in the upper half of the leaves; costa single, strong, percurrent; upper leaf cells subquadrate to quadrate, 6–8 µm wide, with slightly thickened walls; median cells short-rectangular, 6–8 µm x 5–6 µm; basal cells near margins rectangular, 25–30 µm x 8–10 µm, hyaline, thin-walled; basal juxtacostal cells elongate, 30–45 µm x 7–8 µm. Autoicous. Perichaetial leaves similar to the upper stem leaves. Setae elongate, (8–)10–15 mm long, yellow or yellowish brown, twisted above; capsules erect, often two or three per perichaetium, oblong-ellipsoid to oblong-cylindric, 2.5–3.0 x 0.4–0.5 mm, yellow to yellowish brown; annuli well developed, consisting of 1–2 rows of thick-walled cells; peristome teeth reddish brown, lanceolate to linear-lanceolate, 2–3 cleft to the base, densely papillose; opercula with a long, erect beak. Calyptrae mitrate, reaching to the middle or lower part of the capsule, plicate, lobed at the base. Spores spherical, yellowish brown, 10–14 µm in diameter, densely papillose.

Type. U.S.A.: California, H. N. Bolander s.n. (isotypes FH, NY).

Chinese specimens examined: GUIZHOU: Fan-jing Shan (Mt.), C. Gao & J.-Y. Feng 33625 (IFSBH), Tan 91-895 (FH); Kweiting et Tuyun, Handel-Mazzetti 10664 (H); Sui-yang Co., C. Gao & J.-Y. Fen 33566 (IFSBH), Tan 91-681 (FH); Tschenning-Huangtsauba, Handel-Mazzetti 10394 (H); Tuyun et Patschai, Handel-Mazzetti 10734 (H). HEBEI: East Tomb, C.-Y. Yang 604 (BM); Xin-long Co., J.-J. Xia 8350 (IFSBH). HUBEI: Shen-nong-jia (Mt.), C.-Y. Guan 80-2612 (PE), 1980 Sino-Amer. Exped. 523a (as P. linearifolium, NY), 715a (as P. formosicum, NY), 715a (as P. longisetum, NY); Zhong-yang (Changyang), Henry 7482 (BM). HUNAN: Hsin-hwa, Hande-Mazzetti 11770 (as P. polyphylloides fo. longiseta, H); Sang-zhi Co., D.-K. Li 1851 (SHM). JIANGSU: Yi-xing Co., M. Zang 591 (HKAS). SHAANXI: Kuan-tou-san, Giraldi 1850 (BM, H); Miao-wang-san, Giraldi 1358 (H, NY); Tai-bai Shan (Tae-pei-san), Giraldi 1844 (BM, H, NY); Sao-y-san, Giraldi 1353 (H); Zhu-zi, M.-X. Zhang 467 (as P. dentatum, IFSBH). Shanxi: Huo Shan (Ku San), Father Hugh 244 (BM). SICHUAN: Chong-qin City, P.-C. Chen 28 (PE); De-rong Co., X.-J. Li 81-2819 (HKAS); Lei-po Co., P.-C. Chen 5886 (PE); Li Co., Allen et al. 6783 (MO), X.-J. Li 927 (HKAS); Ma-er-kang Co., B.-H. Hu 9 (PE); Omei Shan (Mt.), S.-M. Yu 709 (HKAS); Nan-chuan Co., T. Cao & Q. Li 41519 (IFSBH); Song-pan Co., Redfearn 35318 (NY, SMS); Wo-long, X. Yu 13900 (HKAS); Xiang-cheng Co., J.-L. Yang 4411 (PE); Xi-kang Co., Q.-W. Wang 5724 (PE); Yen-yuen Co., Handel-Mazzetti 2479 (as P. tortula, H); Zhuo-ke-ji Co., Redfearn 351356 (as P. tortula, NY, SMS). TAIWAN: Ilan Co., C.-I. Peng 83-18 (MO). XIZANG: Bo-mi Co., Z.-X. Tan 13147 (IFSBH), Cha-yu Co., M.-Z. Wang 12847d (PE); Lang Co., M. Zang 1828 (HKAS); Ling-zhi Co., S.-K. Chen 337 (PE); Mi-lin Co., K.-Y. Lang 312d (PE); Xin-ba Co., M. Zang 1372 (HKAS); Yi-gong Co., M. Zang 76-72 (HKAS). YUNNAN: Da-li Co., Handel-Mazzetti 6487 (BM, H); De-qin Co., L.-S. Wang 81–1748 (HKAS); Gong-shan Co., M.-Z. Wang 8959 (PE); Kun-ming City, Magill et al. 7514 (MO); Li-jiang Co., Handel-Mazzetti 3091 (H, MO), X.-J. Li 85405 (HKAS); Mei-lish, M. Zang 8654 (HKAS); Men-kong, Handel-Mazzetti 1460 (as P. polyphylloides fo. robustum, BM, H); Wei-xi Co., D.-C. Zhang 655 (HKAS). ZHEJIANG: Lin-an Co., H.-C. Tan 6134 (PE).

Habitat: on boulders, rocks, or thin soil over rocks in mountains, sometimes on rocks along streams, rarely on tree trunks; Distribution: China, Japan, and western North America.

The present species is distinctive in having: 1) robust, multi-branched, fasciculate plants; 2) lanceolate to linear-lanceolate leaves with an ovate or oblong, strongly plicate base and keeled acumen; 3) recurved lower margins and strongly and remotely toothed upper margins; 4) oblong-ellipsoid to oblong-cylindric capsules; and 5) mitrate calyptrae that reach to the middle or lower part of the capsule. Ptychomitrium gardneri is very closely related to the European P. polyphyllum, but it differs from the latter by having more robust plants, with broader, more strongly plicate leaf bases and more acutely dentate upper leaf margins. Ptychomitrium gardneri shows some variations in its leaf form and peristome. The leaf bases are generally ovate to broadly ovate, but some are oblong. The length of the leaf upper part is also variable, especially in some Chinese specimens. Some of the Chinese plants have long-linear upper leaf portions, which are similar to those of the P. gardneri var. angustifolium from Japan. The peristome teeth are normally elongate, linear-lanceolate and coarsely papillose. However, some specimens from China have short, lanceolate, and finely papillose peristome teeth. Ptychomitrium gardneri has a disjunctive eastern Asian and western North American distribution. Its total range has been discussed and well illustrated by T. Cao and Vitt (1994).

Illustrations: Pl. 141, figs. 1–12.