Streamside Sphagnum

Sporophytes are uncommon in Sphagnum riparium. This species is typically very easily recognized in the field with its pale green color, strong terminal bud, and unranked branch leaves.

Plants grayish or yellowish green, in loose tufts. Stem cortex in 2–3 layers, hyaline cells thin-walled, without fibrils and pores; central cylinder not much differentiated from cortical layers, pale yellowish green. Stem leaves 0.9–1.3 mm × 1.0–1.1 mm, triangular-ligulate or broadly ligulate, cucullate-concave, lacerate at the apex; borders rather wide on both sides, clearly widened near the base, ca. 1/3 the leaf width; hyaline cells rarely divided in the upper half, often divided in the lower half. Branches in fascicles of 4–5, with 2–3 spreading. Branch leaves 0.8–1.2 mm × 0.5–0.8 mm, ovate-lanceolate; margins strongly involute in the upper half, truncate, denticulate at the apex; hyaline cells fibrillose, with pores at the opposite ends of upper cells on the ventral surface, often with large, central pores on the dorsal surface; green cells in cross section triangular, exposed on the dorsal surface, enclosed by hyaline cells on the ventral surface. Dioicous; antheridial branches brownish. Perigonial leaves narrow at base, broader upward, abruptly pointed at the apex, borders wide. Perichaetial leaves large, elliptic, cells not dimorphous, sometimes with green cells only, hyaline cells without fibrils and pores. Sporophytes not seen.

Plants stiff and upright, large; green to pale green to brownish, capitulum large and flat, with a conspicuous terminal bud. Stems pale green, superficial cortex of 3-4 layers of weakly differentiated cells. Stem leaves triangular-lingulate, 1.2-1.4 mm; apex with a deep lacerate split; hyaline cells aporose, efibrillose and often septate. Branches unranked to rarely 5-ranked, branch leaves only weakly undulate, but sharply recurved at the apex, leaves not much elongated at distal end. Branch fascicles with 2 spreading and 2 pendent branches. Branch stem green, cortex enlarged with retort cells. Branch leaves ovate-lanceolate; 2-2.6 mm; straight; weakly undulate but strongly recurved, hyaline cells on convex surface with very large irregular pores (formed from the confluence of several smaller pores) at the cell apex, concave surface with large round wall thinnings in the cell angles; chlorophyllous cells triangular to trapezoidal in transverse section, apex normally slightly exposed on concave surface. Sexual condition dioicous. Spores 22-28 µm; proximal surface noticeably papillose, distal surface smooth or with fewer papillae; proximal laesura more than 0.5 the length of the radius.

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

Habitat: usually in open bogs, or on wet ground under coniferous forests.

Sphagnum intermedium var. riparium (Ångstr.) Braithw., Monthly Microscop. J. 13: 62. 1875. Sphagnum intermedium Hoffm. ssp. riparium (Ångstr.) Lindb., Musci Scand. 12. 1879.