Pohlia nutans
Pohlia ludwigii
nodding pohlia, nodding thread-moss, pohlia moss
ludwig's pohlia moss, ludwig's thread-moss
0.5–3.5(–10) cm.
0.8–3.5 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, lanceolate to broadly lanceolate, 1.2–2.4 mm;
base long-decurrent;
margins serrulate to serrate in distal 1/3;
costa subpercurrent;
distal medial laminal cells rhombic to rhomboidal, 40–80 µm, walls firm to thin.
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 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 90–180°, brown to stramineous, broadly pyriform, neck 1/3 urn length;
exothecial cells short-rectangular, walls weakly to moderately sinuate;
stomata superficial;
annulus present;
operculum bluntly conic;
exostome teeth yellow to brown, triangular-acute;
endostome hyaline, basal membrane to 1/2 exostome length, segments tapered apically, distinctly keeled, broadly perforate, cilia short to long.
16–22 µm, finely to distinctly roughened.
14–21 µm, finely roughened.
asexual reproduction typically absent.
asexual reproduction absent.
Pohlia nutans
Pohlia ludwigii
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 ludwigii is a rare alpine species, often found in habitats similar to those of P. obtusifolia and characterized by strongly decurrent leaves that are often slightly cucullate apically. The older lower leaves generally have a pink to reddish tinge. The leaf apices are acute to bluntly acute; the endostome segments are papillose; and the perichaetial leaf costae are very strong at their bases. In late snowmelt areas, P. ludwigii can form deep cushions when sterile.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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