Didymodon australasiae
Didymodon tectorum
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 appressed to weakly spreading when dry, spreading but stiff and not keeled when moist, monomorphic, deltoid to deltoid-lanceolate, grooved adaxially along the costa, especially near leaf apex, 1–1.5(–2) mm, base squared in shape, margins strongly recurved or revolute to near apex of leaf, entire, apex narrowly obtuse, not fragile, commonly ending in a mucro;
costa short-excurrent as a several-celled blunt mucro, not strongly spurred, little widened toward apex, little tapering, sometimes rather thick and bulging adaxially, lacking a adaxial thin-walled pad of cells or this poorly developed, adaxial costal cells quadrate to short-rectangular, 4(-6) cells wide at mid leaf, guide cells in 1(–2) layers;
basal laminal cells differentiated medially or across the leaf, walls mostly thin, quadrate to short-rectangular, not perforated;
distal laminal cells 7–10 µm wide, 1:1, nearly smooth or papillae simple or 2-fid, 2–3 per lumen, lumens quadrate or rounded-quadrate, walls weakly convex on both sides of lamina, distal leaf margins 1-stratose or occasionally 2-stratose in patches.
0.7–1 cm.
0.8–1 cm.
1–1.9 mm;
peristome teeth 32, linear, weakly twisted, to 600 µm, occasionally rudimentary.
1.5–2.5 mm;
peristome teeth 32, linear, twisted 1/2 to once, to 1300 µm.
11–15 µm.
11–12 µm.
asexual reproduction by multicellular tubers on proximal rhizoids.
asexual reproduction by axillary, multicellular gemmae.
laminal KOH reaction variously negative or yellow- or orange- or red-brown.
laminal KOH reaction negative or weakly red.
Didymodon australasiae
Didymodon tectorum
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.)
Although Didymodon brachyphyllus may occasionally lack the usual dense reddish cast in nature or even with KOH, D. tectorum is always green in nature (though weakly red-brown proximally) (R. H. Zander and R. Ochyra 2001). Didymodon luridus Hornschuch of Europe is similar but does not have the squared leaf base, is evenly narrowed to the mucro, and has leaf cells that are smooth or nearly so. The lanceolate leaves of D. vinealis distinguish it from this species though small plants rarely may have gemmae. One collection (New Mexico: E. B. Bartram 99, US) is similar in its stout costa to European material of D. cordatus Juratska. The cells on the adaxial surface of the costa are elongate in some European plants of D. cordatus but quadrate in others in the same collection.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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