Didymodon vinealis
Didymodon fallax
didymodon moss, soft-tuft beard-moss
didymodon moss, false beard-moss, false green-beard moss
leaves often twisted, appressed to weakly spreading or spreading-flexuose when dry, spreading to spreading-recurved and not keeled when moist, monomorphic, lanceolate, grooved adaxially along the costa, especially near leaf apex, 0.8–2.5(–4) mm, base scarcely differentiated to oblong in shape, margins recurved below mid leaf or to above mid leaf, entire, apex acute, not fragile, commonly ending in a conical cell;
costa percurrent or more commonly short-excurrent, not strongly spurred, not much widened or tapering, lacking an adaxial pad of cells, adaxial costal cells quadrate to short-rectangular, ca. 4 cells wide at mid leaf, guide cells in 1(–2) layers;
basal laminal cells differentiated medially or across the leaf, walls thin to weakly thickened, rectangular or seldom quadrate, not perforated;
distal laminal cells 7–10 µm wide, 1:1, nearly smooth or papillae simple or 2-fid, 2–3 per lumen, lumens irregular or oval to rounded-quadrate, walls thin or evenly thickened, convex on both sides of lamina, 1-stratose or occasionally 2-stratose in patches.
leaves appressed to weakly spreading when dry, spreading to spreading-recurved and keeled when moist, monomorphic, ovate-triangular to lanceolate, adaxially grooved along costa, 0.6–2(–2.5) mm, base scarcely differentiated in shape to ovate, margins nearly plane to recurved at mid leaf, entire, apex acute, not fragile;
costa short-excurrent in an often papillose mucro, tapering and considerably wider at the base, pad of cells absent, adaxial costal cells elongate, 2–4 cells wide at mid leaf, guide cells in 1 layer;
basal laminal cells little differentiated, walls usually thickened, quadrate or very short-rectangular;
distal laminal cells 13–15 µm wide, 1:1, papillae absent or simple, 1–3 centered over lumens, lumens usually rounded and often angular, walls thin to irregularly thickened, convex on both sides, 1-stratose.
0.8–1 cm.
0.6–1.2 cm.
1.5–2.5 mm;
peristome teeth 32, linear, twisted 1/2 to once, to 1300 µm, occasionally rudimentary or absent.
0.8–1.5 mm;
peristome teeth 16, linear, cleft to near base, twisted counterclockwise once or occasionally twice, 800–1500 µm. Spores 7–9 µm. Distal laminal KOH reaction red-or yellow-brown, occasionally orange-brown.
9–12 µm. Distal laminal KOH reaction light to dark red-brown, occasionally deep red-orange.
asexual reproduction very rare, by multicellular gemmae in clusters in leaf axils.
asexual reproduction specialized structures absent.
Didymodon vinealis
Didymodon fallax
Varieties 2 (2 in the flora).
Didymodon vinealis is often difficult to distinguish from sterile forms of D. rigidulus, but the elongate cells commonly found on the adaxial surface of the costa near the boat-shaped leaf apex, the often strongly papillose laminal cells, and the usual presence of a distinct groove down the adaxial surface of the leaf along the costa are characteristic features. Some but not all specimens may be quickly assigned to this taxon by a unique deep slit floored by elongate cells on the adaxial surface of the costal apex (the adaxial epidermis being absent), visible as a clear window abaxially. Bryoerythrophyllum recurvirostrum is immediately distinguished by the clear, enlarged proximal cells. Like Bellibarbula recurva, small forms of D. vinealis may have quadrate or very short-rectangular proximal cells and sinuose costa, but the former has thick-walled proximal cells and the costa twists laterally, not vertically in the concave distal portion of the leaf of D. vinealis, and the adaxial cells of the costa of commonly elongate, 2:1 or more.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
In Didymodon fallax, the elongate cells on the adaxial surface of the costa and the usually rounded lumens of the distal laminal cells are characteristic. Hymenostylium recurvirostrum is similar in these respects and could be mistaken for D. fallax when sterile, but that species lacks a stem central strand (at least in temperate areas) and the median laminal cells are larger than those of the marginal. Ditrichum flexicaule may be mistaken for this species but has rather strongly serrulate distal margins and is always clear yellow in KOH, never with an orange cast. Didymodon asperifolius is similar in general morphology but has quadrate or short-rectangular adaxial costal cells. Didymodon fallax intergrades to some extent with D. ferrugineus and D. maximus. Thick laminal cell walls are correlated with lack of papillae in all these species. Robust collections from hyperoceanic areas, e.g., Newfoundland and British Columbia, with long (to 2.5 mm) leaves and proximally very broad costae (to 150 µm) have much the appearance of the European D. spadiceus (Mitten) Limpricht, but differ by the long (to 800 µm) twisted peristome and margins recurved commonly to near the apex. The leaves of D. fallax, being somewhat keeled though not strongly recurved, have the grooved costa of D. vinealis but plants may be placed correctly by the elongate adaxial costal cells. Ceratodon purpureus may be mistaken for D. fallax, but the former has a deep, clear yellow color in KOH solution and weakly serrulate distal leaf margins.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Peristome present, well developed, cells of operculum twisted | var. vinealis |
1. Peristome absent, cells of operculum straight or nearly so | var. rubiginosus |
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