Sphagnum girgensohnii
Sphagnum arcticum
common green peat-moss, Girgensohn's sphagnum
arctic sphagnum
leaves lingulate, broadly lingulate to lingulate-spatulate; 0.8–1.3 mm, apex broad, truncate and lacerate, border broad at base (more than 0.25 of base);
hyaline cells rhomboid, efibrillose, and rarely septate.
leaves narrowly to broadly lingulate or sometimes lingulate-spatulate, (1.1–)1.2–1.4(–1.6) mm;
apex broadly obtuse to obtuse-truncate and more or less fimbriate-lacerately resorbed, border in distal half narrow and often indistinct, in proximal half widened and filling up 1/3–1/2(–2/3) of the breadth at the base;
hyaline cells broadly S-shaped to rhombic S-shaped, predominantly nonseptate but a few cells are 1–3-septate;
efibrillose.
typically long and tapering, not 5-ranked.
unranked, terete.
ovate to ovate-lanceolate, 1–1.4(–1.8) mm, concave, straight, apex strongly involute, margins entire;
hyaline cells on convex surface with numerous elliptic pores along the commissures, grading from small pores near the apex to large pores near the base, concave surface with large round pores along the margins and base.
broadly lanceolate to ovate-lanceolate, (1.1–)1.4–1.8(–2.1) mm, slightly concave, straight to slightly subsecund;
apex involute;
border entire;
hyaline cells on convex surface with (5–)8–10(–12) semicircular to elliptical, ringed pores along the commissures, concave surface aporose or infrequently with 1–2 pores per cell in the distal portion of the cell, more numerous along leaf margins.
dioicous.
unknown.
21–27 µm, moderately to coarsely papillose on both surfaces;
proximal laesura less than 0.5 spore radius.
not seen.
fascicles with 2 spreading and 1–2 pendent branches.;
branch stem with solitary retort cells or in groups of 2–3, necks moderately distinct.
fascicles with 2 spreading and 1 pendent branch.
Sphagnum girgensohnii
Sphagnum arcticum
Sporophytes are uncommon in Sphagnum girgensohnii. This species is most frequently associated with S. russowii, but also found growing with S. centrale, S. fallax, S. fimbriatum, S. warnstorfii, and S. magellanicum when growing in shaded sites of mires. It is very similar to S. rubiginosum, but S. girgensohnii lacks any reddish pigments, has only 2 spreading branches per fascicle, infrequently produces sporophytes, and differs in spore morphology. Throughout much of its range, S. girgensohnii is readily recognized by its green color and its large, slender, strongly stellate capitulum. In the more northern portion of its range, it frequently forms compact stands with a golden brown color and then the stem leaf must often be examined for accurate identification. In Alaska it overlaps morphogically with S. fimbriatum subsp. concinnum, which can look very similar but will have a more spatulate stem leaf that is lacerate completely across the broad flat apex and slightly down the sides. Sphagnum girgensohnii, on the other hand, has stem leaves only lacerate for about 3/4 of the apex width and less conspicuously broadened at the apex.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Sporophytes are uncommon in Sphagnum arcticum. All collections of this fairly common species have been made north of 59° N latitude in wet or moist tundra vegetation. In its typical dark brown color, this species is often quite distinctive in the field. Sphagnum fuscum is smaller, not as dark, and its stem leaves are not as truncate-lacerate. Sphagnum subfulvum has a glossy sheen, which S. arcticum lacks, and its stem leaf has an obtuse but not lacerate apex.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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