4. Bryum arcticum (R. Brown.) Bruch & Schimp. in B.S.G. 极地真藓 ji di zhen xian
Bryol. Eur. 4: 154. f. 335. 1846. Pohlia arctica R. Brown, Chlor. Melvill. 38. 1823. Type: Canada.
Bryum alpicola Broth., Symb. Sin. 4: 57. 1929. Type: China. Sichuan, Mu-li Co., Handel-Mazzetti 7403.
Plants small to large, up to 50 mm high, usually reddish, in tufts. Stems rarely branched. Leaves oblong-ovate to ovate-lanceolate, up to 1.7 mm long, abruptly acute, reddish at base; margins recurved, usually entire; costae long-excurrent, reddish below; branch leaves imbricate, ovate, cucullate; median leaf cells hexagonal, 38–45 µm × 15–22 µm, thin-walled; marginal cells narrowed, indistinctly bordered by 1–2 rows of linear cells; basal cells rectangular. Synoicous. Setae 7–10 mm long, reddish brown; capsules pendulous, clavate (club-shaped) to oblong-pyriform, 1.5–2.2 mm long; neck shorter than urn; stomata present; exostome teeth yellowish brown, finely papillose; endostome segments linear or rudimentary; basal membrane ca. 1/2 the height of teeth; cilia short or absent. Spores 20–25 µm in diameter.