Didymodon johansenii

(R. S. Williams) H. A. Crum

Canad. Field-Naturalist 83: 157. 1969,.

Basionyms: Barbula johansenii R. S. Williams Rep. Canad. Arct. Exped., Moss. 4, figs. 1–12. 1921
Treatment appears in FNA Volume 27. Treatment on page 545. Mentioned on page 540, 546, 547.

Plants green to reddish green. Stems to 1.5 cm, central strand present. Stem-leaves erect-appressed when dry, spreading and not keeled when moist, monomorphic, oblong-lanceolate, adaxially weakly concave across leaf, 0.7–1.1 mm (excluding the deciduous tip) to 2.5 mm whole, base scarcely differentiated in shape, margins recurved at mid leaf, entire, apex thickened, long-cylindric to clavate, seldom a long, filiform excurrency, usually soon deciduous, constricted in places, absent in mature leaves; costa excurrent, excurrency absent in mature leaves, not much widened or tapering at mid leaf but swollen in excurrency, pad of cells absent, adaxial costal cells elongate at mid leaf but quadrate near apex, 2–4 cells wide at mid leaf, guide cells in 1 layer; basal laminal cells differentiated medially, walls thin; distal laminal cells 13–15 µm wide, 1: 1, papillae absent, lumens often angular, walls thin to irregularly thickened, weakly convex on both sides, 1-stratose except in deciduous apex. Specialized asexual reproduction by the deciduous leaf apex. Seta 0.35–0.50 cm. Capsule 0.75–1.00 mm; peristome teeth 16, linear, cleft to near base, straight to weakly twisted, ca. 200 µm. Spores 15–18 µm. Distal laminal KOH reaction red.


Phenology: Capsules mature summer (Jul–Aug).
Habitat: Limestone outcrops and cliffs, boulder crevices, slopes, tundra, alluvial plain forest
Elevation: moderate to high elevations (1400-1600 m)

Distribution

V27 781-distribution-map.gif

Alta., N.W.T., Nunavut, Yukon, Alaska, Europe, Asia (China)

Discussion

Distinctive characters of Didymodon johansenii are the striate peristome teeth, deciduous, clavate leaf apex and large, trigonous laminal cells. Most collections of it lack the propaguliform apex in all but the most immature leaves, and the leaves are oblong-lanceolate. Some specimens (e.g., Northwest Territories: Scotter 22404, MICH), however, approach D. ridigulus var. icmadophilus in the green color, ovate leaf base, and apparently nondeciduous leaf apices. These collections can be rightly placed by the presence of claviform apices in at least some leaves (especially those near an inflorescence) and the large distal laminal cells, which often have trigones. Didymodon nigrescens has fragile, clavate tips to its perichaetial leaves, but the crenulate distal leaf margins and very thin costa will distinguish it.

Selected References

None.

Lower Taxa

None.

"um" is not declared as a valid unit of measurement for this property."um" is not declared as a valid unit of measurement for this property.

... more about "Didymodon johansenii"
quadrate +  and elongate +
0.3 cm3 mm <br />0.003 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
channeled +, concave +  and long-triangular +
0.04 cm0.4 mm <br />4.0e-4 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
of 1-2 rows +  and differentiated +
long-excurrent +  and short-excurrent +
deciduous +
2 (?) +  and 4 (?) +
Richard H. Zander +
(R. S. Williams) H. A. Crum +
weak +  and strong +
ovate +  and crescent--shaped +
papillose +  and smooth +
usually slightly wider +
differentiated +
differentiated +
Barbula johansenii +
obovoid +
cucullate +
stegocarpous +
0.075 cm0.75 mm <br />7.5e-4 m <br /> (0.1 cm1 mm <br />0.001 m <br />) +
monoicous +, dioicous +  and sexual +
flat to bulging +
thin;thick +
1 (?) +  and 10 (?) +
hexagonal +
tomentose +  and bare +
quadrate +  and rectangular +
occasionally weakly dentate or crenulate +  and entire +
subquadrate;hexagonal or rounded-angular occasionally shortly rectangular or rhomboid +
Alta. +, N.W.T. +, Nunavut +, Yukon +, Alaska +, Europe +  and Asia (China) +
moderate to high elevations (1400-1600 m) +
differentiated +
tapering +  and filiform +
constricted +
multicellular +
occasional +
Limestone outcrops and cliffs, boulder crevices, slopes, tundra, alluvial plain forest +
yellow +  and orange-red or red +
0.07 cm0.7 mm <br />7.0e-4 m <br /> (0.11 cm1.1 mm <br />0.0011 m <br />) +
concave;oblong-lanceolate;keeled +
ovate +, keeled +  and curled +
reduced +
specialized +
dioicous +  and sexual +
occasionally trigonous +  and weakly strongly convex +
short-conic;long-conic +
photosynthetic +
solid +  and simple +
lateral +  and terminal +
lateral +  and terminal +
red +, orange +  and yellow +
oblong +  and linear or long-triangular +
Capsules mature summer (Jul–Aug). +
1 (?) +  and 2 (?) +
Canad. Field-Naturalist +
straight +
yellowish;reddish-brown +
elongate +
0.35 cm3.5 mm <br />0.0035 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
2 +  and 1 +
rounded-triangular +  and rounded-pentagonal +
0 cm0 mm <br />0 m <br /> (1.5 cm15 mm <br />0.015 m <br />) +
Barbula sect. Acutae +, Barbula subsect. Acutiformes +, Barbula sect. Asteriscium +, Barbula sect. Fallaces +, Barbula subsect. Fallaciformes +, Barbula sect. Graciles +, Barbula sect. Rubiginosae +, Barbula sect. Vineales +, Barbula subsect. Vinealiformes +, Dactylhymenium +, Didymodon sect. Asteriscium +, Didymodon sect. Fallaces +, Didymodon sect. Graciles +, Didymodon sect. Vineales +, Geheebia +, Husnotiella +  and Trichostomopsis +
Didymodon johansenii +
Didymodon +
species +
elliptic;cylindric +
0.1 cm1 mm <br />0.001 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
rudimentary +
red +  and yellow +
specialized +
thin +  and irregularly thickened +
stemless +  and perigoniate +
green;reddish green +