Pohlia nutans
Pohlia robertsonii
nodding pohlia, nodding thread-moss, pohlia moss
0.5–3.5(–10) cm.
0.5–1 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, 1.3–1.6 mm;
margins serrulate to serrate in distal 1/3;
costa subpercurrent;
distal medial laminal cells irregularly hexagonal to rhomboidal, 70–120 µm, walls thin to firm.
orange to orange-brown.
multiple, orange-brown.
paroicous, rarely dioicous;
perigonial leaves ovate-lanceolate;
perichaetial leaves somewhat differentiated, ± long-lanceolate.
paroicous;
perichaetial leaves scarcely differentiated, 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 10–45°, stramineous to orange-brown, long- and slender-pyriform, neck 3/4–1 time urn length;
exothecial cells elongate-rectangular, walls slightly sinuate;
stomata superficial;
annulus present;
operculum long-conic;
exostome teeth orange-yellow to brown, bluntly acute;
endostome hyaline to yellow-brown, basal membrane low, scarcely exceeding capsule rim, segments narrow, keeled basally, not or slightly perforate, cilia absent or rudimentary.
16–22 µm, finely to distinctly roughened.
16–20 µm, ± finely but distinctly roughened.
asexual reproduction typically absent.
asexual reproduction absent.
Pohlia nutans
Pohlia robertsonii
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 robertsonii, known only from Monterey County, is the only North American polysetous species of Pohlia. The leaves are less dull in appearance than those of P. elongata and P. nutans, but not notably shiny like those of P. cruda or P. longicolla; they are more like the moderately glossy leaves often seen in P. bolanderi. The laminal cells have firm but not thick walls, thinner-walled than in P. elongata and P. nutans, shorter and less vermicular than in P. cruda or P. longicolla. Sporophytes are produced abundantly on the paroicous gametophytes. The exostome teeth are rather irregular and poorly developed, not gradually tapered to narrow acute apices, and the endostome segments are narrow, scarcely keeled, and narrowly or not at all perforate.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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