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BFNA
Title: Sphagnaceae |
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Editoral Note: Asterisks
are inserted to control placement of the dot in the dot maps. Other codes
should be self-explanatory. 2. SPHAGNACEAE Dumortier Cyrus B. McQueen Richard E. Andrus Plants with branches in fascicles, branches
usually of spreading and pendent types but rarely spreading only. Protonemata
thallose. Leaves usually of two distinctly different types; branch leaves
that are normally inrolled and broadest ca. 1/4--1/3 the distance from the
base, more or less tapered to a cucullate to involute apex; stem leaves more
or less flat and usually broadest at the base; both leaf types of a network
of hyaline, dead cells and green chlorophyllose cells; pores and reinforcing
fibrils frequent in branch leaf hyaline cells and uncommon in stem leaf
hyaline cells. Rhizoids lacking. Sporophyte consisting of a spherical
capsule with pseudostomata on capsule surface, a very short seta, and a foot,
exserted on a pseudopodium of gametophyte tissue. Spores
released by explosive opening of operculum. The sphagnum mosses, or peat mosses, are not only unique
morphologically but also ecologically.
With their abundant clear cells they can retain up to 25 times their
dry weight in water, and a uniquely powerful acidifying power permits
sphagnum to direct succession wherever conditions are suitable for them to
flourish. Much of the earth’s surface
with a cool humid climate is dominated, thus, by sphagnum peatlands. Genus 1, species ca. 285 (89 species
in the flora): nearly worldwide. 1. SPHAGNUM Linnaeus, Sp. Pl. 2: 1106. 1753 * [Greek
sphagnos, an unknown plant] Plants typically with upright stems, young
branches arranged spirally around stem at growing apex into a capitulum,
branches clustered into fascicles along stem, stem and branch leaves of
alternating inflated, S-shaped to rhomboid hyaline cells and narrow linear
chlorophyllous cells, hyaline cells typically fibrillose and porose on branch
leaves. Protonema typically 1-stratose, gametophyte developing from
lateral margin. Stems differentiated into a central cylinder of thin-walled
parenchymatous cells, merging into a cylinder of thick-walled cortical cells
surrounded by 0--4 layers of thin-walled inflated cells, superficial layer of
cells usually aporose, but may be porose.
Stem leaves may be less
fibrillose or efibrillose and less porose or aporose than the branch leaves,
often septate, a distinct border of narrow linear chlorophyllous cells often
along margins and at base, and with a greater width:length ratio than branch
leaves in anisophyllous forms, partly differentiated in hemiisophyllous
forms, and identical in isophyllous forms.
Branches typically
dimorphic as spreading and pendent branches, but some species lack branches
or branches are not clearly differentiated, pendent branches typically more
slender than spreading branches and with a tendency to adhere to and cover
the stem. Branch fascicles typically with 2 spreading and 1--2 pendent
branches, but there may be up to 12(--14) per fascicle. Branch
stems typically green, with a superficial layer of inflated retort cells;
these grouped or solitary, usually porose at the distal end with a
conspicuous or inconspicuous neck. Branch leaves with 2/5 phyllotaxy, of
a 1-stratose network of alternating chlorophyllous and hyaline cells; hyaline
cells usually S-shaped, rarely rhomboid, nearly always strengthened with conspicuous
spiral fibrils, small to large, round to elliptic and sometimes ringed pores
occur along commissures or rarely on cell lumen, convex surface typically
with more pores per cell than concave surface; chlorophyllous cells may be
enclosed on both surfaces, more broadly exposed on one surface or equally
exposed on both surfaces as viewed in transverse section, adjacent cell walls
typically smooth, but various types of cell wall projections may be clearly
visible in transverse section. Sexual condition dioicous or
monoicous; stalked globose antheridia borne at the tips of branches usually
with swollen colored tips of branches near capitulum; long-necked archegonia
borne on short branches singly surrounded by perichaetial leaves that are
typically longer than branch leaves. Capsule spherical, brown to black, lacking
an annulus or peristome with a operculum convex; spore sac amphithecial in
origin, over-arching columella. Calyptra membranous. Spores
tetrahedral, with prominent trilete mark, fine to coarse superficial surface,
distal surface may have raised Y-mark, bifurcated Y-mark sculpture, or none. Species 250 (89 in the flora); primarily in boreal regions but also
in cool, moist montane and oceanic habitats such as nutrient-poor and acidic
wetlands and mires; worldwide in distribution excepting Antarctica. The concept of species in the genus is controversial. We have followed the lead of P. Isoviita
(1966) and K. I. Flatberg (1994) in the recognition of species. H. A. Crum (1984) and others (R. E. Daniels
and A. Eddy 1985; A. L. Andrews 1958, 1959) have adopted more conservative
taxonomic species concepts for species in the Northern Hemisphere. Discussion of the spores above is from T.
Cao and D. H. Vitt (1986); for additional discussion of the protonema see C.
McQueen (1988). Microscopic features can be observed by using a concentrated aqueous
or alcohol solution of Crystal Violet.
A 50% solution of alcohol and Methylene Blue or Safranin Red can be
used, but these usually do not stain features such as minute pores, fibrils,
wall thinnings, and surface sculpture on the chlorophyllous cells. The number and kinds of branches should be
determined, individual stem and branch leaves (from the middle of a spreading
branch) should be examined from the distal 2 cm of the plant, and the
superficial surface of stem cortical cells may need examination as well as do
cross sections of branch leaves and stems. SELECTED REFERENCES Andrus, R. E. 1980. Sphagnaceae (Peat Moss Family) of New York
State. New York State Mus. Bull. 442. Crum, H. A. 1984. Sphagnopsida, Sphagnaceae. North
American flora, Series II, Part 11. New
York Botanical Garden, Bronx, New York. Daniels,
R. E. and A. Eddy. 1990. Handbook of European Sphagna. Institute of
Terrestrial Ecology, Huntingdon. Flatberg,
K. I. 2002. The Norwegian Sphagna: A field colour guide. NTNU Vitenskapsmuseet Rapp. Bot. Ser. 2002--1: 1--44 + 54 plates. Isoviita, P. 1966. Studies on Sphagnum L. 1. Nomenclatural
revision of the European taxa. Ann.
Bot. Fennici 3: 199--264. McQueen, C.
B. 1990. Field Guide to the peat mosses of Boreal
North America. London. Nyholm, E. 1969. Illustrated moss flora of Fennoscandia II. Musci 6: 647--799. Lund. 1. Outer stem cortical cell
walls reinforced with spiral fibrils 1. Outer stem cortical cell
walls smooth. 2. Outer cortical cells of branches
nearly all porose at distal end; branch leaves with denticulate margins and
bordered with resorption furrow 2. Outer cortical cells of branches
of two kinds, smaller aporose cells and larger retort-shaped cells with pore
at apical end; branch leaf margins usually entire. 3. Fascicles of 7 or more
branches 1h. Sphagnum
sect. Polyclada, p. XXX 3. Fascicles of 6 or fewer
branches. 4. Branch leaf hyaline cells
efibrillose, but see S. splendens in sect. Cuspidata 4. Branch leaf hyaline cells
fibrillose. 5. Branch and stem leaves
isophyllous; branches in fascicles of 2--3, spreading and pendent branches
similar, or plants may have single or no branches; hyaline cells of branch
leaves usually with numerous pores along the commissures, giving a bead-like
appearance; chlorophyllous cells of branch leaves in transverse section
barrel-shaped, truncate-elliptic to trapezoidal, exposed equally on both
surfaces or slightly more broader on the convex surface 5. Branch and stem leaves
usually anisophyllous; 3--6 branches per fascicle, spreading branches clearly
differentiated from pendent branches; hyaline cells of branch leaves with
scattered pores along the commissures; chlorophyllous cells of branch leaves
in transverse section triangular, truncate-trapezoidal to elliptical and may
be more broadly exposed on either surface. 6. Branch leaf chlorophyllous
cells triangular to trapezoidal, exposed much more broadly on concave or
convex surface 7. Chlorophyllous cells of
branch leaves triangular to trapezoidal in transverse section, more broadly
exposed on the convex surface; in plants with stellate capitula, the branches
between the rays of the capitulum occur in pairs; stem leaves often hanging
downward on the stem 7. Chlorophyllous cells of
branch leaves triangular to trapezoidal in transverse section, more broadly
exposed on the concave surface; in plants with stellate capitula, the
branches between the rays of the capitulum single; stem leaves upright on the
stem............... 1i. Sphagnum sect. Acutifolia, p. XXX 6. Branch leaf chlorophyllous cells lenticular, truncate-elliptic to trapezoidal;
exposed more or less equally on both surfaces or slightly more broadly on
convex surface. 8. Stem leaves with apex broad
and fimbriate; branch leaves often squarrose from an enlarged clasping base; interior
surface of chlorophyllous cells often finely papillose. 1d. Sphagnum sect. Squarrosa, p. XXX 8. Stem leaves with apex
obtuse and entire to erose; branch leaves straight, slightly subsecund, or
slightly recurved; interior surface of chlorophyllous cells always smooth. 9. Branch leaves with broad
truncate toothed apex, hyaline cells with pores in cell ends and angles 9. Branch leaves with rounded,
untoothed or weakly toothed apex, hyaline cells on convex surface with
numerous pores along commissures 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 onthickened. Sexual
condition usually dioicous. Capsule 2 mm or more. Spores
typically 22--30 \um, distal surface sculpture may be present; proximal
laesura usually more than 0.5 spore radius. Species 54 (12 in the flora): worldwide in distribution
excepting Antarctica. 1. Branch leaf chlorophyllous
cells in transverse section more or less equilateral-triangular, often with
conspicuous vertically oriented comb-fibrils on the hyaline cells where
overlying chlorophyllous cells. 2. Branch cortical cells with funnel-like
projections often extending halfway or more into the next cell; branches strongly
clavate and blunt 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. 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 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. Stem leaf hyaline cells
with distinct comb-lamellae; branches clavate andpointed; branches leaves
strongly imbricate 4. Stem leaf hyaline cells
with distinct comb-lamellae; branches not clavate; branch leaves more or less
spreading. 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 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 12. Sphagnum steerei 1. Branch leaf chlorophyllous
cells in transverse section narrowly triangular, trapezoidal,
truncate-elliptic, elliptic or lenticular; comb-fibrils if present
horizontally oriented. 6. 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 short-elliptic and well enclosed; plants purplish
red when pigmented 7. Branch leaf chlorophyllous
cells in transverse section narrowly elliptic and slightly enclosed on both
surfaces; plants brown when pigmented. 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 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.................. 4.
Sphagnum
centrale 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. Branch leaf hyaline cells
where overlying chlorophyllous cells papillose............................................... 9. Sphagnum papillosum 9. Branch leaf hyaline cells
where overlying chlorophyllous cells epapillose. 10. Superficial stem cortical
cells with fibrils weak or lacking; chlorophyllous cells rectangular to truncate-elliptic,
exposed equally on both surfaces............ 10.
Sphagnum
perichaetiale. 10. Superficial stem cortical
cells with strong fibrils; chlorophyllous cells triangular exposed more
broadly on concave surface. 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........................... 5. Sphagnum
henryense 11. Branch leaf hyaline cells
smooth throughout; pores on the convex surface elliptic to flattened-elliptic,
not numerous 1. Sphagnum affine Renauld
& Cardot, Rev. Bryol. 12: 44. 1885 Sphagnum imbricatum
subsp. affine (Renauld &
Cardot) Flatberg; S. imbricatum var. affine (Renauld & Cardot) Warnstorf; S. imbricatum var. laeve Warnstorf Plants moderate-sized and lax to somewhat
compact, +/- stiff-stemmed; moderate-sized to large, forming lawns or low,
loose hummocks; green, yellow-brown to golden-brown and often tinged with
brown to purplish brown; capitulum +/- flat in lax open-grown forms to +/-
rounded and compact in open grown forms.
Stems brown, superficial
cortical layer with spiral reinforcing fibrils clearly visible, usually 2 or
more pores per cell, comb-fibrils visible on interior wall. Stem
leaves to 1.3--1.9 x 0.6--1.2 mm; rarely hemiisophyllous; hyaline cells
non-ornamented, nonseptate or sometimes septate. Branches
+/- tapering, leaves loosely imbricate to spreading and often squarrose in
shade forms. Branch fascicles with 2 spreading and 2--3 pendent branches. Branch
stems with cortical cell comb-lamellae weakly differentiated on interior wall,
no or weak funnel-like projections on the interior end walls, pores in superficial
wall mostly restricted to leaf attachments.
Branch leaves ovate to
ovate elliptical, 1.5--2 x 0.9--1.6 mm; hyaline cells on convex surface with
elliptic to more often round pores along the commissures, comb-lamellae can
be present, but often absent or restricted to leaf bases; chlorophyllous
cells broadly triangular in transverse section and well-enclosed on the
convex surface; end wall not thickened.
Sexual condition dioicous. Capsule
with scattered pseudostomata . Spores 27--31 \um; granulate on both
surfaces; laesura on proximal surface less than 0.5 the spore radius. Widespread and often ruderal, wide variety of minerotrophic wetlands,
especially abundant in forested mires; Nfld. and Labr. (Nfld.), N.S., P.E.I.;
Ala., Ark., Conn., Del., D.C., Fla., Ga., Ill., Ind., Ky., La., Maine, Md.,
Mass., Miss., Mo., N.H., N.J., N.Y., N.C., Ohio., Okla., Pa., S.C., Tenn.,
Tex., Vt., Va., W.Va.; Europe. Capsules fairly common, mature early to late summer. This species may occur elsewhere but the
taxonomy is unclear (K. I. Flatberg 1984).
Although species of Sphagnum
sect. Sphagnum are notoriously
difficult to tell apart in the field, S.
affine is typically smaller than S. centrale,
S. palustre, and S. papillosum,
the other brown species of this section with which it may occur. It is also much more likely to have
somewhat squarrose branch leaves, especially in shade forms. |