Didymodon brachyphyllus
Didymodon nigrescens
black beard moss, black didymodon moss
leaves appressed to weakly spreading when dry, spreading but stiff and not keeled when moist, monomorphic, ovate to ovate-lanceolate, grooved adaxially along the costa, often cucullate near leaf apex, 0.7–1 mm, base scarcely differentiated to ovate in shape, margins weakly recurved to near apex of leaf, entire, apex broadly acute or blunt, not fragile, often ending in 1–3 celled apiculus;
costa ending shortly before the apex or percurrent, seldom weakly excurrent, often weakly spurred, little widened towards apex, little tapering, sometimes rather thick and bulging adaxially, lacking an 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 somewhat thickened, weakly convex on both sides of lamina, distal leaf margins 1-stratose or occasionally 2-stratose in patches.
leaves appressed when dry, spreading and not keeled when moist, monomorphic, long-ovate to lanceolate, broadly concave adaxially across leaf, usually 0.8–1.7 mm, base weakly differentiated in shape, long-ovate, margins usually broadly recurved to revolute to mid leaf or to near apex, minutely crenulate, apex acute to narrowly acuminate, often weakly cucullate;
costa percurrent or ending 2–4 cells below the apex, little tapering, not strongly spurred, without an adaxial pad of cells, adaxial costal cells rectangular, 2 cells wide at mid leaf grading to 4 below, guide cells in 1 layer;
basal laminal cells differentiated medially, walls thick, rectangular, not perforated;
distal laminal cells in rows, 7–11(–14) µm wide, 1:1 or often longitudinally elongate, papillae apparently absent but visible in section as low, flattened to multiplex capitulate lenses, 1–3 per lumen, lumens ovate, walls evenly thickened and weakly convex on both sides of lamina, 1-stratose.
0.8–1 cm.
0.7–0.9 cm.
1.5–2.5 mm;
peristome teeth rudimentary or 32, linear, twisted 1/2, 200–250 µm, delicate and commonly coming off with the operculum.
1.5–2.8 mm;
peristome teeth 32, linear, straight to twisted 1.5 times, 100–600 µm. Spores 9–13 µm. Distal laminal KOH reaction red.
10–13 µm. Distal laminal KOH reaction yellow- or red-brown.
asexual reproduction by axillary, multicellular gemmae.
asexual reproduction absent.
Didymodon brachyphyllus
Didymodon nigrescens
A largely arid land species, Didymodon brachyphyllus, has an ovate leaf shape, margins only moderately recurved, and costa ending before the apex, which may terminate in a small conical cell or apiculus. Propagula are not always produced. Although the KOH reaction is commonly red, it may be yellow but not negative, as in D. tectorum. Didymodon luridus Sprengel (see R. H. Zander 1978e) does not occur in the flora area, though reported from there by many authors (often as D. trifarius, see Zander 1981). It differs in the triangular leaves and the smooth, more homogeneous and smaller distal laminal cells, 6–9 µm. American collections identified as this species are commonly actually D. brachyphyllus, D. nicholsonii, D. tophaceus, or D. vinealis. Small forms of D. nicholsonii have the leaf shape of D. brachyphyllus but the lamina is 2-stratose. Sterile Grimmia species are similar, but a small hyaline apex is commonly found on at least some Grimmia leaves. Small forms of D. vinealis may be confused with D. brachyphyllus but the latter never has lanceolate leaves, and its perichaetial leaves are also short and rather deltoid. Didymodon tectorum is similar but has larger leaves, usually green in nature, broadly rectangular leaf base, and an excurrent costa. Didymodon revolutus is similar but has unicellular gemmae. The exsiccat N. Amer. Musci Perf. 404, distributed by A. J. Grout as Husnotiella torquescens, is D. brachyphyllus with operculate sporophytes having rudimentary peristomes.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
The specimens cited as Didymodon nigrescens from the Firth River Basin by W. C. Steere (1978), determined by R. H. Zander, are actually Didymodon subandreaeoides. The distinguishing characters of D. nigrescens are the blackish coloration when dry (red in KOH), thin costa and distal laminal margins minutely crenulate by the small, bulging marginal cells. This and the following two species appear to be closely related by the rather distinctive crenulation of the leaf apices. Didymodon asperifolius is similar but may be distinguished by its longer leaves, straight or reflexed to strongly recurved when wet, distal margins recurved and smooth, distal laminal cells larger, 10–13 µm wide, epapillose or papillae simple, costa usually rather wide.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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