Didymodon australasiae
Didymodon tophaceus
didymodon moss, olive beard-moss, olive green-beard moss
leaves spreading-incurved and twisted to incurved-appressed when dry, spreading to spreading-recurved and not keeled when moist, monomorphic, short-lanceolate or sometimes short-ovate to long-elliptic, broadly concave adaxially across leaf, usually 1–2.5 mm, base scarcely differentiated in shape to ovate, margins usually recurved at mid leaf, entire, apex broadly acute or occasionally narrowly so, not fragile;
costa percurrent or ending a few cells below the apex, broader at mid leaf, occasionally weakly spurred, with a low adaxial pad of cells, adaxial costal cells quadrate, 4–6 cells wide at mid leaf, guide cells in 1–2 layers;
basal laminal cells differentiated medially or across leaf, quadrate to short-rectangular, walls very thin and not perforated;
distal laminal cells 7–12 wide, 1:1 or occasionally transversely elongate below, papillae usually distinct, low or simple to 2-fid, occasionally absent, lumens oval to rounded-quadrate, walls thin to evenly thickened, convex on both sides of lamina, 2-stratose in one or more rows along margins.
leaves weakly spreading or rarely appressed when dry, spreading and often keeled when moist, monomorphic, ovate to long-elliptic but occasionally ovate-lanceolate, adaxially grooved along costa or broadly channeled, 1–2 mm, base ovate, margins recurved in proximal 3/4 of leaf and often decurrent on stem, entire, apex broadly acute to obtuse or rounded, often in same collection, not fragile;
costa percurrent or ending 1–6 cells below the apex, tapering or rarely spurred above, sometimes much broadened at the base, pad of cells absent, adaxial costal cells elongate at least in the central 2 rows, 4 cells wide at mid leaf, guide cells in 1 layer;
basal laminal cells weakly differentiated medially, quadrate or short-rectangular, walls usually thickened;
distal laminal cells 9–12(–14) µm wide, 1:1, papillae usually absent, rarely simple and 1–2 per lumen, lumens rounded-quadrate or rounded, walls thin to thickened, weakly convex on both sides, 1-stratose.
0.7–1 cm.
0.7–1.2 cm.
1–1.9 mm;
peristome teeth 32, linear, weakly twisted, to 600 µm, occasionally rudimentary.
0.6–1.5 mm;
peristome teeth absent, rudimentary or short and 16, ligulate, cleft to near base, untwisted, to 220 µm.
11–15 µm.
12–14(–20) µm.
asexual reproduction by multicellular tubers on proximal rhizoids.
asexual reproduction specialized structures absent.
laminal KOH reaction variously negative or yellow- or orange- or red-brown.
laminal KOH reaction red- to orange-brown, occasionally yellow-brown.
Didymodon australasiae
Didymodon tophaceus
In North American Didymodon, hydroids are found in the costae of D. anserinocapitatus, D. australasiae, D. nevadensis, D. norrisii, D. umbrosus, D. revolutus, and D. vinealis, and in these species the adaxial stereid band is usually absent in well developed specimens. Intergrades exist between D. australasiae and D. umbrosus, but the extreme forms are common and quite distinctive.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Insufficient emphasis has been placed on the elongate cells of the adaxial costal surface of Didymodon tophaceus. The similar European D. sicculus Cano, Ros, García-Zamora & J. Guerra, with quadrate adaxial costal cells (M. J. Cano et al. 1996), should be looked for in the flora area. Although long leaf decurrencies are often considered characteristic of D. tophaceus, these are not always present. Being rather variable, this species is sometimes difficult to distinguish from the lanceolate-leaved D. fallax. It is commonly fruiting but absent from the Arctic. Like fellow calciphilic hygrophiles Hymenostylium recurvirostrum and Eucladium verticillatum, D. tophaceus is often encrusted with calcium carbonate; the broad leaves and often red costa help distinguish the latter. Barbula bolleana is quite like D. tophaceus but can be immediately distinguished by its large size, the 20–30 even rows of thin-walled, often papillose distal laminal cells with quadrate to short-rectangular lumens, and the peristome when present long and twisted, while D. tophaceus has 10–15 often irregular rows of usually thick-walled, usually smooth distal laminal cells with usually oval lumens, and a short peristome. The western D. nicholsonii has much the same leaf shape and hygrophytic nature but differs by the less decurrent leaves with 2-stratose margins or patches (or distally throughout), the smaller, more papillose laminal cells, which are red in KOH (D. tophaceus may be red-tinged but the laminal cell walls are yellow under the high-power lens), and the quadrate adaxial costal cells (in surface view). Because of its broadly rounded leaf apices, Barbula convoluta may be confused with D. tophaceus, but it is very bright yellow in KOH solution, has small, strongly papillose laminal cells, and is not hygrophilic.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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