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FNA | Family List | FNA Vol. 27 | Sphagnaceae | Sphagnum

1a. Sphagnum Linnaeus sect. Sphagnum

Plants typically large, with distinct capitulum; green, pale green, yellowish, red, tan, brown to dark brown. Stems green, brown or reddish, outer cortex of 3-4 layers of inflated, thin-walled cells, superficial cells with conspicuous to faint spiral fibrils, no or strong ornamention on interior wall, and 1-6 round to ovate pores per cell. Stem 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. Branches dimorphic, spreading branches tumid, pendent branches usually shorter and more slender. Branch 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. Branch leaves 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. Sexual condition usually dioicous. Capsule 2 mm or more. Spores typically 22-30 µm, distal surface sculpture may be present; proximal laesura usually more than 0.5 spore radius.

Species 54 (12 in the flora): worldwide except Antarctica.

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)
+ Branch leaf chlorophyllous cells in transverse section narrowly triangular, trapezoidal, truncate-elliptic, elliptic or lenticular; comb-fibrils if present horizontally oriented   (6)
       
2 (1) Branch cortical cells with funnel-like projections often extending halfway or more into the next cell; branches strongly clavate and blunt.   11 Sphagnum portoricense
+ 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 (2) Interior layer of stem cortical cells with distinct comb-lamellae; branch leaves with or without comb-lamellae; stem leaves without comb-lamellae.   1 Sphagnum affine
+ 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 (3) Stem leaf hyaline cells with distinct comb-lamellae; branches clavate and pointed; branches leaves strongly imbricate.   3 Sphagnum austinii
+ Stem leaf hyaline cells without distinct comb-lamellae; branches not clavate; branch leaves more or less spreading   (5)
       
5 (4) 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.   6 Sphagnum imbricatum
+ 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.   12 Sphagnum steerei
       
6 (1) Branch leaf chlorophyllous cells in transverse section short-elliptic, elliptic to lenticular, and enclosed on both surfaces   (7)
+ 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 (6) Branch leaf chlorophyllous cells in transverse section short-elliptic and well enclosed; plants purplish red when pigmented.   7 Sphagnum magellanicum
+ Branch leaf chlorophyllous cells in transverse section narrowly elliptic and slightly enclosed on both surfaces; plants brown when pigmented   (8)
       
8 (7) 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   2 Sphagnum alaskense
+ 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.   4 Sphagnum centrale
       
9 (6) Branch leaf hyaline cells papillose where overlying chlorophyllous cells.   9 Sphagnum papillosum
+ Branch leaf hyaline cells epapillose where overlying chlorophyllous cells   (10)
       
10 (9) Superficial stem cortical cells with fibrils weak or lacking; chlorophyllous cells rectangular to truncate-elliptic, exposed equally on both surfaces.   10 Sphagnum perichaetiale
+ Superficial stem cortical cells with strong fibrils; chlorophyllous cells triangular, exposed more broadly on concave surface   (11)
       
11 (10) 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.   5 Sphagnum henryense
+ Branch leaf hyaline cells smooth throughout; pores on the convex surface elliptic to flattened-elliptic, not numerous.   8 Sphagnum palustre

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