Sphagnum angustifolium C. E. O. Jensen 1896

The sporophytes of Sphagnum angustifolium are somewhat common. This species is distinguished from similar ones in sect. Cuspidata by the small, triangular, obtuse and appressed stem leaves. It also often has a pink stem, as opposed to the reddish branch bases seen in some other species of the section. Sphagnum balticum has stem leaves that are more lingulate-triangular as well as spreading from the stem. Sphagnum angustifolium belongs to a subgroup within sect. Cuspidata usually referred to as S. recurvum, in the broad sense, a group of mostly carpet-forming species that differ from other members of the section in having pairs of pendent branch buds visible between the capitulum rays. The group also includes S. brevifolium, S. fallax, S. flexuosum, S. pacificum, S. recurvum, S. rubroflexuosum, and S. splendens.

Plants small, green to yellowish brown; capitula often small, not distinct radiate. Stem cortex in 1 layer, sometimes not well developed, hyaline cells lacking fibrils; central cylinder yellowish green. Stem leaves 0.5–0.8 mm × 0.5–0.7 mm, flat, nearly equilateral-triangular, slightly dentate or erose at a broadly acute apex; borders differentiated, slightly widened at the base; hyaline cells lacking fibrils, only divided at leaf base, generally without pores. Branch leaves ca. 1.1–1.4 mm × 0.3–0.4 mm, lanceolate, crowded and imbricate, spirally arranged when moist, not or only slightly undulate when dry, dentate and truncate at the apex; green cells in cross section triangular, exposed on the dorsal surface, slightly reaching the ventral surface; hyaline cells with large pores at the upper ends and a few small pores at the corners and along commissures on the dorsal surface, those from pendent branch leaves with numerous pores on the ventral surface. Dioicous. Sporophytes not seen.

Plants small and often slender and soft, lax to compact, moderately stiff-stemmed; green to pale yellow to golden brown to brown; capitulum strongly convex in drier grown forms to strongly 5-radiate and flat in wetter growing forms. Stems pale green to pale brown, often with pinkish red patches, cortex undifferentiated. Stem leaves equilateral to isosceles-triangular, small, less than 0.8 mm, mostly appressed to stem, apex acute to obtuse, hyaline cells efibrillose and nonseptate. Branches straight to slightly curved, usually 5-ranked; leaves not much longer at distal end than proximal end. Branch fascicles with 2 spreading and 2-3 pendent branches. Branch stems with cortex enlarged with conspicuous retort cells, often pinkish red at proximal end. Branch leaves narrowly ovate-lanceolate, 0.8-1 mm, straight, moderately undulate and recurved in larger and/or wetter grown forms, not undulate and slightly recurved in compact forms from drier sites; margins entire; hyaline cells on convex surface with 1(2-3) pore per cell at apical end of cell, on concave surface with round wall thinnings in cell ends and angles; chlorophyllous cells triangular in transverse section and just enclosed on concave surface. Sexual condition dioicous. Spores 21-25 µm; coarsely papillose on proximal and distal surfaces; proximal laesura more than 0.5 spore radius.

Distribution: China, Korea, Japan, Russian Far East, Europe, and North America.

Habitat: in peatland under open forests.

Sphagnum recurvum var. angustifolium Warnstorf, Nyt. Mag. Naturvidensk. 31: 213. 1888; S. amblyphyllum var. parvifolium (Sendtner) Warnstorf; S. flexuosum var. tenue (H. Klinggraff) Pilous; S. parvifolium (Warnstorf) Warnstorf; S. recurvum var. parvifolium Warnstorf; S. recurvum var. tenue H. Klinggraff

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Sphagnum angustifolium, the fine bogmoss, is a species of peat moss with a Holarctic distribution.