2. Arctoa hyperborea (With.) Bruch & Schimp in B. S. G., Bryol. Eur. 1: 87 (fasc. 33–36, Mon. 3, 2). 1846; Bryum hyperboreum Gunn. ex With., Syst. Arr. Brit. Pl. ed. 4, 2: 811. 1801.
Plants slender, 1–5 cm high, brownish green, shiny, in dense tufts. Stems erect, simple or forked, radiculose only at the base. Leaves in many rows, 3–5 mm long, erect-patent, upper parts reflexed or secund, narrowed from an oval-lanceolate base to a subulate apex; margins entire or somewhat serrulate only at the apex; costa slender, occupying 1/8 – 1/6 the leaf base width, ending near the apex or shortly excurrent; leaf cells incrassate throughout, upper cells irregularly rounded-quadrate or short-rectangular, less than 2:1; lower cells slightly elongate; alar cells distinctly differentiated, nearly quadrate to short-rectangular. Setae stout, purple, 5–8 mm long; capsules erect, oblong-obovoid, 1.5 × 1.0 mm, symmetric or nearly so, with 8 striate when dry; annuli developed, and deciduous; opercula obliquely rostrate; peristome teeth not spreading when dry, divided halfway down, often striate. Spores green, ca. 30 µm in diameter, finely papillose.
Chinese specimens examined: HEILONGJIANG: Tang-yuan Co., S.-E. Liu 1461 (MO). JILIN: An-tu Co., C. Gao 22432 (IFSBH), 22454 (MO). SICHUAN: Mi-ya-luo, Z. Wang et al. 3710 (IFSBH). XIZANG: Mo-tou Co., Y.-G. Su 957 (a) (IFSBH, KUN).
Habitat: on soil, humus or rocks in forests; Distribution: China, Russia, Europe, and North America.
Illustrations: C. Gao (ed.) 1994 (Pl. 104, figs. 1–10).