Didymodon rigidulus
Didymodon asperifolius
rigid didymodon moss
didymodon moss, rough-leaf beard-moss, rough-leaf green-beard moss
leaves appressed-incurved to weakly spreading when dry, spreading or not and not keeled when moist, monomorphic, long-ligulate, ovate-lanceolate, elliptic-lanceolate or long-lanceolate, broadly channeled across leaf or occasionally somewhat channeled along costa, 0.8–1.7(–3) mm, base scarcely differentiated to ovate, margins recurved in proximal 1/4–3/4, entire, apex acute to subulate, occasionally fragile;
costa percurrent to excurrent as a long, thick, blunt subula, not much widened or tapering through the leaf, not strongly spurred, lacking a bulging adaxial pad of cells, adaxial costal cells quadrate, in (2–)3–4(–5) rows, guide cells in a single layer;
basal laminal cells weakly differentiated medially, rectangular, walls thin to evenly thickened, proximal maginal cells little differentiated;
distal laminal cells mostly 8–11 µm wide, 1:1, papillae absent or simple or occasionally 2-fid, lumens oval to rounded-quadrate, walls evenly thickened, moderately bulging on both sides or only abaxially, sometimes 2-stratose marginally or at apex of leaf, or throughout lamina.
leaves appressed-incurved when dry, usually strongly recurved and keeled when moist, monomorphic, triangular to lanceolate, adaxially grooved along costa, 1.2–2.5 mm, base ovate, margins strongly and broadly recurved in proximal 1/2 or up to near apex, entire, apex narrowly to broadly acute, not fragile, commonly ending in a conical cell;
costa percurrent or ending 1–4 cells before the apex, tapering, widened pad of cells absent, adaxial costal cells quadrate to short-rectangular, 4–6 cells wide at mid leaf, guide cells in 1 layer;
basal laminal cells differentiated medially or across leaf, rectangular, walls usually thickened;
distal laminal cells 13–15 µm wide, 1:1, papillae usually absent, rarely simple, weak and domelike, 1 per lumen, lumens rounded or angular, walls thickened, often irregular or very weakly trigonous, weakly to strongly convex on both sides, 1-stratose.
0.7–1.7 cm.
0.4–0.6 cm.
1–2 mm;
peristome teeth 32 or 16 cleft to base or rudimentary or occasionally absent, filamentous or long-triangular, straight or weakly twisted, to 740 µm. Spores 9–12 µm. Distal laminal KOH reaction yellow- or red-orange.
ca. 1 mm;
peristome teeth 16, short-lanceolate to linear, irregularly cleft or perforate to near base, straight, to 50–300 µm. Spores 13–15 µm. Distal laminal KOH reaction red.
asexual reproduction by axillary, ovate to elliptic, multicellular gemmae.
asexual reproduction specialized structures absent.
Didymodon rigidulus
Didymodon asperifolius
Varieties 6 (5 in the flora).
Didymodon rigidulus in the broad sense, as emended by R. H. Zander (1981b) is polymorphic, with several varieties distinguished by fairly good correlations of combinations of characters. Specimens of intermediate morphology that are not clearly assignable to any one variety may be identified as D. rigidulus in the broad sense. Although some authors use the presence of axillary gemmae as diagnostic of the typical variety, other varieties, notably var. gracilis, may occasionally have them. Such gemmae are also found in other species, especially those of the D. vinealis complex. Didymodon vinealis may have 2-stratose distal laminal cells, and should be carefully distinguished.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Didymodon asperifolius can sometimes be immediately recognized by a red-yellow translucency in leaves of dry plants, like oiled paper. The adaxial surface of the costa may have either quadrate or short-rectangular cells. The distal laminal cells are also rather large for the genus. The KOH reaction, as well as the natural color of the lamina are sometimes light orange, but usually quite red. Some plants may appear green but the laminal cell walls are red under high magnification.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Lamina 2-stratose in distal 1/2-3/4 | var. subulatus |
1. Lamina 1-stratose or 2-stratose only at the extreme leaf apex or on the distal margins | → 2 |
2. Leaves oblong-lanceolate, elliptic-lanceolate or occasionally long-triangular; costa usually short-excurrent and blunt; apex and distal margins generally 2-stratose; gemmae often present | var. rigidulus |
2. Leaves short-lanceolate to lanceolate; costa percurrent to long-excurrent, usually sharp; distal margins 1-stratose or less commonly 2-stratose in patches; gemmae usually absent | → 3 |
3. Plants flagellate, leaves strongly appressed when dry, linear-lanceolate; costa long-excurrent | var. ditrichoides |
3. Plants thickly leaved, leaves appressed to spreading when dry, short-lanceolate to long-lanceolate; costa percurrent to long-excurrent | → 4 |
4. Leaves short- to long-lanceolate; base evenly broadened, square or rectangular; costa usually percurrent to short-excurrent as a rigid subula, seldom-excurrent; distal cells generally papillose, oval or rounded-quadrate; proximal cells short-rectangular; gemmae occasionally present | var. gracilis |
4. Leaves long-lanceolate; base abruptly broadened, ovate; costa usually long-excurrent as a straight or flexuose, often fragile subula; distal cells usually smooth, usually angular; proximal cells usually quadrate; gemmae very rare | var. icmadophilus |
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