Pohlia nutans
Pohlia obtusifolia
nodding pohlia, nodding thread-moss, pohlia moss
blunt-leaf pohlia, blunt-leaf thread-moss, obtuseleaf pohlia moss
0.5–3.5(–10) cm.
0.3–0.8 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, broadly lanceolate, 0.7–1.4 mm;
margins serrulate to serrate in distal 1/3;
costa subpercurrent;
distal medial laminal cells hexagonal or broadly rhombic, lax, 30–70 µm, walls thin.
orange to orange-brown.
orange-brown.
paroicous, rarely dioicous;
perigonial leaves ovate-lanceolate;
perichaetial leaves somewhat differentiated, ± long-lanceolate.
paroicous;
perichaetial leaves scarcely differentiated, broadly 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 160–180°, stramineous to orange-brown, broadly pyriform, neck 1/3 urn length;
exothecial cells elongate-rectangular, walls straight;
stomata superficial;
annulus present;
operculum bluntly conic;
exostome teeth yellow to brown, bluntly acute;
endostome hyaline, basal membrane low, scarcely exceeding capsule rim to 1/3 exostome length, segments narrow, weakly keeled, broadly perforate, cilia absent.
16–22 µm, finely to distinctly roughened.
17–25 µm, distinctly roughened.
asexual reproduction typically absent.
asexual reproduction absent.
Pohlia nutans
Pohlia obtusifolia
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.)
Plants of Pohlia obtusifolia with sporophytes are generally small, but some sterile colonies in late snowmelt areas at high elevations form deeper cushions. When plants are sterile, the subtly cucullate leaves provide a clue to their identity; they are similar to those of P. drummondii, but the stems tend to be less red, the laminal cells are broader and thinner walled, and axillary gemmae are absent. Pohlia obtusifolia is paroicous (unlike P. drummondii, which is dioicous) and the capsules are barrel-shaped, with straight, rectangular walls (sinuate in P. drummondii and other gemmiferous species). The peristome of P. obtusifolia is relatively reduced, with slenderly triangular exostome teeth that are weakly pitted basally, a low endostomial basal membrane, and narrow segments that are weakly keeled but broadly perforate.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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