Russow's Sphagnum

Sporophytes are uncommon in Sphagnum russowii. This species is associated with S. centrale, S. fallax, S. fimbriatum, S. girgensohnii, and S. squarrosum. Because of its not particularly distinct phenotype as well its strong tendency to produce hemiisophyllous stem leaves, S. russowii is probably the most frequently misidentified Sphagnum species. The combination of the flat, stellate capitulum, unranked branch leaves, and lingulate stem leaf will usually suffice to identify it. Sphagnum capillifolium has a rounded capitulum and a pointed stem leaf while S. subtile also has a rounded capitulum but a shorter and more triangular stem leaf. In montane and arctic mires it can be confused with S. warnstorfii but the latter usually has conspicuously 5-ranked branch leaves. As one might expect in such a widespread and common species, the characters can vary considerably. For example, one regularly finds plants that are consistent in every respect with the description except that they lack stem cortical pores. Some stem leaves have almost no septations in the hyaline cells while other forms have most of the cells septate. As with similar variation in the likewise common S. fuscum, there is no consistent pattern and so taxonomic recognition of the variants is unwarranted.

This species is quite common in southwestern and northeastern China. It often occurs in large, dense cushions producing sporophytes. The branch leaves of this species are similar to those of Sphagnum squarrosum with reflexed leaf apices, but it differs from the latter in having smaller, slender, and softer plants with tightly imbricate branch leaves.

Plants ± moderate-sized, stiff and open, compact on exposed sites, capitulum flat-topped and often stellate; green or variegated red and green, lacking metallic sheen when dry. Stems typically mixed green and red; superficial cortical cells mostly rectangular and uniporose with a single round to ovate pore in distal portion of cell usually free from cell wall, some cells and occasionally whole stems may be aporose. Stem leaves lingulate, 1.3-1.6 mm, apex broadly rounded or pointed and notched (sometimes denticulate), border strong and broadened at base (more than 0.25 width); hyaline cells short sinuoid-rhombic, mostly efibrillose, 0-1(-2)-septate. Branches long and slender, never 5-ranked. Branch fascicles with 2 spreading and 1-2 pendent branches. Branch leaves ovate-lanceolate, 1.3-1.6 mm, concave, straight, apex strongly involute; hyaline cells on convex surface with numerous round to elliptic pores along the commissures, grading from small round pores near the apex to large elliptic pores at the base, concave surface usually with large round pores throughout, but sometimes restricted to proximal portions of leaf. Sexual condition dioicous, but some specimens apparently monoicous. Spores 18-33 µm, coarsely papillose on both surfaces; proximal laesura more than 0.5 spore radius.

Plants variable in size and color, stout or slender, soft, pale green or yellow, tinged with reddish color, in dense cushions. Stem cortex in 2–4 layers, hyaline cells without fibrils, with a large pore in each cell; central cylinder pale yellowish or reddish. Stem leaves 0.8–1.3 mm × 0.6–0.9 mm, variable in size, usually broadly ligulate, rounded, denticulate or somewhat lacerate at the apex; borders narrow above, suddenly widened near the base; hyaline cells rhomboidal, usually undivided, without fibrils and pores, or rarely with the traces of fibrils and small pores in the upper cells. Branches in fascicles of 4–5, with 2–3 spreading. Branch leaves 0.8–1.6 mm × 0.5–0.9 mm, ovate-lanceolate, gradually to abruptly acuminate, reflexed near the apex when dry, blunt and denticulate at the apex; margins involute, cucullate above, borders differentiated; hyaline cells with pores at the corners in the upper cells and numerous pores here and there on the ventral surface, with elliptic pores at the opposite ends along commissural rows on the dorsal surface; green cells in cross section isosceles-triangular or trapezoidal, exposed more broadly on the ventral surface, enclosed by hyaline cells on the dorsal surface or slightly exposed on both surfaces. Dioicous or monoicous; antheridial branches purple red. Perigonial leaves similar to vegetative branch leaves. Perichaetial leaves broadly ovate, blunt at the apex, borders indistinct, with hyaline and green cells in the upper half, with almost only green cells in the lower half, hyaline cells without fibrils. Spores yellowish, smooth, 21–32 µm in diameter.

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

Habitat: usually on wet humic soil under coniferous forests; also in bogs and on ground near streams.

Sphagnum acutifolium var. robustum Russow

Sphagnum acutifolium Schrad. var. robustum Russ., Arch. Naturk., Liv-Ehst-Kurlands, Ser. 2, Biol. Naturk. 7: 117. 1865, hom. illeg. Sphagnum acutiforme Schlieph. & Warnst. var. robustum Warnst., Flora 67: 501. 1884. Sphagnum robustum (Warnst.) Röll, Flora 69: 109. 1886.