Sphagnum sect. Squarrosa

(Russow) Schimper
Syn. Musc. Eur. ed. 2, 835. 1876,.
Basionym: Squarrosa Russow Beitr. Torfm., 33. 1865
Treatment appears in FNA Volume 27. Treatment on page 58. Mentioned on page 47, 60.

Plants moderate-sized to robust, with distinct capitulum; green,yellowish brown. Stems green to dark reddish brown, superficial cortex of 2–4 layers of efibrillose, non-ornamented, enlarged, thin-walled, aporose, rectangular cells. Stem leaves ovate, ovate-lingulate to lingulate; with broad, fringed apex; little or no border along margins or base; hyaline cells rhomboid, efibrillose, non-ornamented, aporose, usually nonseptate, with resorption gaps on exterior surface. Branches strongly dimorphic, pendent branches thinner but about same length as spreading branches. Branch stems green, with cortex surrounded by 1–2 layers of efibrillose, non-ornamented, enlarged, thin-walled cells, some cells apically porose with inconspicuous necks. Branch leaves strongly squarrose or spreading, ovate, ovate-hastate or ovate-lanceolate, margins entire, apex involute and smooth; hyaline cells fibrillose; with large, round pores at cell ends and along commissures, sometimes with faint papillae on interior walls; chlorophyllous cells ovate-triangular, elliptical to ovate-elliptical in transverse section, more broadly exposed on convex surface, end walls not thickened. Sexual condition monoicous or dioicous. Capsule 2 mm or more, with scattered pseudomata. Spores less than 30 µm, both surfaces smooth to finely papillose; proximal laesura more than 0.5 spore radius.

Distribution

North America, Eurasia, Pacific Islands (New Zealand).

Discussion

Species 4 (4 in the flora).

Selected References

None.

Key

1 Branch leaves markedly truncate; chlorophyll cells ovate-triangular in transverse section, with the widest part at or near the convex surface. Sphagnum tundrae
1 Branch leaves not truncate; chlorophyll cells elliptical to elliptical-ovate with the broadest part typically some distance from the convex surface > 2
2 Branch leaves strongly squarrose (terete in tundra forms), large (1.9-3 mm); hyaline cells of branch leaves with ringed elliptic pores on concave surface and unringed pores on convex surface; stem leaves 1/2-2/3 as long as branch leaves (1.1-1.9 mm) Sphagnum squarrosum
2 Branch leaves imbricate (squarrose in shade forms), moderate in size (1-1.5 mm); hyaline cells of branch leaves with unringed pores on concave and convex surfaces; stem leaves as long or longer than branch leaves (1-1.7 mm) > 3
3 Branch leaf hyaline cells near leaf base on convex surface mostly aporose and on concave surface with large, faint pores; 1-2 hanging branches. Sphagnum mirum
3 Branch leaf hyaline cells near leaf base on convex surface with large, round pores and on concave surface mostly aporose; 2-3 hanging branches. Sphagnum teres