12. Sphagnum fuscum (Schimp.) Klinggr., Schriften Königl. Phys.-Ökon. Ges. Köningsberg. 13(1): 4. 1872; Sphagnum acutifolium Schrad. var. fuscum Schimp., Mém. Acad. Sci. Sav. Inst. Fr. 15: 64. 1857. S. acutifolium ssp. fuscum (Schimp.) Herib., Mém. Acad. Sci. Clermont-ferrand, sér. 2, 14: 444. 1899.
Plants slender, up to 12 cm high, dark green tinged with brownish color, in compact tufts. Stem cortex in 3–4 layers, hyaline cells thin-walled, without fibrils; central cylinder brownish green or yellowish. Stem leaves 0.8–1.2 mm × 0.5–0.8 mm, slightly larger than or equal to branch leaves, oblong-ligulate, flat, with obtuse, entire or lacerate apex, borders narrow above the middle, suddenly widened below (ca. 1/4 the leaf width at base); hyaline cells divided, generally without fibrils. Branches in fascicles of 3–4, with 2 spreading. Branch leaves 0.8–1.3 mm × 0.4–0.5 mm, ovate-lanceolate, gradually narrowed to a blunt, dentate apex, borders narrowly differentiated, entire, involute above; hyaline cells fibrillose, with several rather large, ringed pores nearly along commissure on the dorsal surface, in the upper cells without pores on the ventral surface, with a few large pores below the middle parts of leaves; green cells often triangular or sometimes trapezoidal, exposed on the ventral surface, enclosed by hyaline cells on the dorsal surface. Dioicous; antheridial branches similar to vegetative branches, yellowish brown. Perigonial leaves small, broadly ovate. Perichaetial leaves large, broadly elliptic. Spores yellowish, smooth, 25–30 µm in diameter.
Chinese specimens examined: HEILONGJIANG: Xiao Xing An Ling (Lesser Khingan Mt.), C. Gao 1052 (IFSBH, KUN, MO), 13022 (IFSBH, MO). NEI MONGOL: Mangui, K.-Y. Zhao s.n. Sept. 30, 1987 (IFSBH, MO).
Habitat: growing in compact hummocks in peatland or on shaded, wet ground under forests; Distribution: China, Japan, Russian Far East, Europe, and North America.
Illustrations: C. Gao (ed.) 1994 (Pl. 5, figs. 1–5).