Pohlia nutans
Pohlia crudoides
nodding pohlia, nodding thread-moss, pohlia moss
pohlia moss
0.5–3.5(–10) cm.
0.4–2.5 cm.
erect to ± spreading, lanceolate to ovate-lanceolate, 2 mm;
base not or scarcely decurrent;
margins subentire or more often serrulate to serrate in distal 1/3;
costa subpercurrent, percurrent, or rarely short-excurrent;
distal medial laminal cells hexagonal to rhomboidal, firm, 50–90 µm, walls moderately thick.
erect to ± spreading, narrowly long-lanceolate, 1–2.2 mm;
margins strongly revolute, serrulate to serrate in distal 1/3;
costa subpercurrent;
distal medial laminal cells linear-hexagonal, 35–80 µm, walls thin, not porose.
orange to orange-brown.
orange-brown.
paroicous, rarely dioicous;
perigonial leaves ovate-lanceolate;
perichaetial leaves somewhat differentiated, ± long-lanceolate.
dioicous;
perigonial leaves broadly short-ovate;
perichaetial leaves moderately differentiated, narrowly lanceolate.
inclined 80–100°, orange to orange-brown, slender-pyriform, neck 1/2 urn length;
exothecial cells elongate-rectangular, walls straight;
stomata superficial;
annulus present;
operculum conic;
exostome teeth yellow to orange-brown, acute-triangular;
endostome hyaline or rarely orange-brown, basal membrane 1/2 exostome length, segments tapered apically, broadly keeled, broadly perforate, cilia short to long.
inclined 30–90°, brown, ovoid-cylindric, neck 1/3 urn length;
exothecial cells short- to long-rectangular, walls straight or weakly sinuate;
stomata superficial;
annulus present;
operculum conic;
exostome teeth whitish to yellow, bluntly acute, coarsely papillose throughout;
endostome whitish to hyaline, basal membrane low, to 1/3 exostome length, segments narrow, scarcely keeled, narrowly or not perforate, cilia absent or rarely rudimentary.
16–22 µm, finely to distinctly roughened.
15–25 µm, finely roughened.
asexual reproduction typically absent.
asexual reproduction absent.
Pohlia nutans
Pohlia crudoides
Pohlia nutans is the most common species of Pohlia in North America, Europe, and elsewhere in the Northern Hemisphere. In contrast to the treatment by A. J. Shaw (1982), P. sphagnicola is not separated here from P. nutans; the type of P. sphagnicola is European. Plants referable to P. sphagnicola, including North American collections, differ in being dioicous and having entire leaves, slightly shorter laminal cells, and smaller spores. The habitat in Sphagnum hummocks is not diagnostic; at least 80% of plants growing in Sphagnum are P. nutans. Pohlia schimperi, a northern form with reddish leaves, also dioicous, is not recognized, as per Shaw.
The peristome of Pohlia nutans is as well developed as any in Pohlia, with long, tapered, trabeculate exostome teeth and well-developed endostomes with broadly keeled, widely perforate segments and short to long cilia. The laminal cells are short- to elongate-hexagonal with thickened walls. The only other North American species with relatively thick-walled laminal cells is P. elongata; the cells of P. elongata are typically longer, but there is extensive overlap in sizes. Plants without sporophytes have generally been named P. nutans, although some collections from montane regions may actually be P. elongata; sporophytes of P. elongata have longer necks, as long as or longer than the urns, and reduced peristomes with endostome segments narrowly split along the keel and (usually) no cilia.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Pohlia crudoides is a distinctive Arctic species characterized by cherry red stems and relatively stiff, dark green leaves with strongly recurved margins. The perichaetial leaves of most Pohlia species have recurved margins, but the only other North American species with strongly recurved vegetative leaf margins is P. cardotii. The latter has shorter, broader leaves with short-rhombic cells often with porose-thickened walls. Pohlia crudoides has weakly tapered exostome teeth coarsely papillose from top to bottom, which give them a whitish appearance under a dissecting microscope; the endostome segments also are papillose.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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