Sphagnum sect. Sphagnum
Sphagnum imbricatum
leaves typically as large as or larger than branch leaves, lingulate to ovate-lingulate with broad rounded apex, border fringed;
hyaline cells rhomboid, efibrillose or fibrillose, sometimes ornamented, aporose, 0–2-septate, and often resorbed on exterior surface.
leaves short-rectangular, 0.8–1.1 mm, hyaline cells mostly non-septate and absent comb-fibrils.
dimorphic, spreading branches tumid, pendent branches usually shorter and more slender.
ovate to broadly ovate, apex cucullate and roughened on convex surface;
margin toothed;
hyaline cells fibrillose;
convex surface pores round to elliptic, usually with 1 at each corner of three adjacent hyaline cells; chlorophyllous cells lenticular to triangular, sometimes with wall ornamentation visible in transverse section; chlorophyllous cells enclosed, equally exposed, or more broadly exposed on concave surface, end walls thickened or unthickened.
ovate to ovate-elliptic, 1.4–1.8 mm;
hyaline cells on convex surface with numerous pores along the commissures;
comb-lamellae obvious only in proximal 1/2 of leaf; chlorophyllous cells broadly triangular in transverse section and well-enclosed on the convex surface.
usually dioicous.
dioecious.
2 mm or more.
typically 22–30 µm, distal surface sculpture may be present;
proximal laesura usually more than 0.5 spore radius.
(22) 24–27(–28) µm, surface granulate.
fascicles with 2–3 spreading branches and 1–3 pendent branches.;
branch stems green, surrounded by 1 layer of enlarged thin-walled cells, typically porose and fibrillose, in some species ornamented on interior wall;
retort cells absent.
fascicles with 2 spreading and 1–2 hanging branches.;
branch stems with hyaline cells non-ornamented, no or weak funnel-like projections on the end walls of cortical cells, cortical cell walls usually with large round pores.
Sphagnum sect. Sphagnum
Sphagnum imbricatum
Species 54 (12 in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
K. I. Flatberg (1984) considered Sphagnum imbricatum to be East Asian in distribution but a recent collection in Selawik National Wildlife Refuge places it in the North American flora. It will undoubtedly be found elsewhere. Sphagnum imbricatum is closest in morphological detail to S. steerei, but the latter is a very dark colored and densely branched species whereas S. imbricatum is quite light in color and not particularly dense.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Branch leaf chlorophyllous cells in transverse section ± equilateral-triangular, often with conspicuous vertically oriented comb-fibrils on the hyaline cells where overlying chlorophyllous cells | → 2 |
1. Branch leaf chlorophyllous cells in transverse section narrowly triangular, trapezoidal, truncate-elliptic, elliptic or lenticular; comb-fibrils if present horizontally oriented | → 6 |
2. Branch cortical cells with funnel-like projections often extending halfway or more into the next cell; branches strongly clavate and blunt. | S. portoricense |
2. Branch cortical cells with flat end walls or with weak funnel-like projections extending less than halfway into the next cell; branches not clavate or if clavate, with pointed ends | → 3 |
3. Interior layer of stem cortical cells with distinct comb-lamellae; branch leaves with or without comb-lamellae; stem leaves without comb-lamellae. | S. affine |
3. Interior layer of stem cortical cells without comb-lamellae or at least not visible with a light microscope; branch leaves with comb-lamellae; stem leaves with or without comb-lamellae | → 4 |
4. Stem leaf hyaline cells with distinct comb-lamellae; branches clavate and pointed; branches leaves strongly imbricate. | S. austinii |
4. Stem leaf hyaline cells without distinct comb-lamellae; branches not clavate; branch leaves more or less spreading | → 5 |
5. Stem leaves short (ca. 0.8-1.1 mm); branch leaves broad (breadth:length ca. 0.7-0.8), branch leaf comb-lamellae usually distinct only in lower half of leaf; branch cortical comb-lamellae present; plants yellow to golden brown. | S. imbricatum |
5. Stem leaves long (ca. 1.1-1.5 mm.); branch leaves narrow (breadth:length ca. 0.6-0.68), branch leaf comb-lamellae distinct throughout most of leaf; branch cortical cell comb-lamellae usually absent; plants dark brown. | S. steerei |
6. Branch leaf chlorophyllous cells in transverse section short-elliptic, elliptic to lenticular, and enclosed on both surfaces | → 7 |
6. Branch leaf chlorophyllous cells in transverse section narrowly triangular, rectangular to truncate-elliptic, exposed equally on both surfaces or more broadly on the convex surface | → 9 |
7. Branch leaf chlorophyllous cells in transverse section short-elliptic and well enclosed; plants purplish red when pigmented. | S. magellanicum |
7. Branch leaf chlorophyllous cells in transverse section narrowly elliptic and slightly enclosed on both surfaces; plants brown when pigmented | → 8 |
8. Branch leaf chlorphyllous cells in transverse section without thickened ends walls; superficial stem cortical cells with reinforcing fibrils weak or absent; branch leaf hyaline cells where overlying chlorophyll cells often with comb-fibrils | S. alaskense |
8. Branch leaf chlorphyllous cells in transverse section with thickened end walls; superficial stem cortical cells with strong reinforcing fibrils; branch leaf hyaline cells where overlying chlorophyllous cells smooth. | S. centrale |
9. Branch leaf hyaline cells papillose where overlying chlorophyllous cells. | S. papillosum |
9. Branch leaf hyaline cells epapillose where overlying chlorophyllous cells | → 10 |
10. Superficial stem cortical cells with fibrils weak or lacking; chlorophyllous cells rectangular to truncate-elliptic, exposed equally on both surfaces. | S. perichaetiale |
10. Superficial stem cortical cells with strong fibrils; chlorophyllous cells triangular, exposed more broadly on concave surface | → 11 |
11. Branch leaf hyaline cells where overlying chlorophyllous cells often with irregular worm-like ridges, especially at the leaf base; pores on the convex surface numerous, small and round to elliptic. | S. henryense |
11. Branch leaf hyaline cells smooth throughout; pores on the convex surface elliptic to flattened-elliptic, not numerous. | S. palustre |
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