Flora of North America species comparison

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Didymodon rigidulus

Didymodon umbrosus

rigid didymodon moss
Habit Plants green, often blackish. Plants usually green to very bright green distally, contrasting with light tan proximally.
Stem(s)

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 spreading-incurved and twisted to incurved-appressed when dry, spreading to spreading-recurved and not keeled when moist, monomorphic, long-lanceolate, broadly concave adaxially across leaf, usually 1–2.5(–4) mm, base sharply differentiated in shape, ovate, margins usually plane, entire, apex narrowly acute, 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 rectangular, 4–6 cells wide at mid leaf, guide cells in 1–2 layers;

basal laminal cells strongly differentiated medially, rectangular, walls very thin or hyaline, often perforated by transverse slits;

distal laminal cells in rather distinct rows, 7–12 wide, 1:1 or occasionally longitudinally elongate, papillae usually absent, lumens oval to rounded-quadrate or rounded-rectangular, walls convex on both sides of lamina, 2-stratose in one or more rows along margins.
Seta

0.7–1.7 cm.

0.7–1 cm.
Capsule

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.

1–1.9 mm;

peristome teeth 32, linear, weakly twisted, to 600 µm. Spores 11–15 µm. Distal laminal KOH reaction variously negative or yellow- or orange- or red-brown.
Specialized

asexual reproduction by axillary, ovate to elliptic, multicellular gemmae.

asexual reproduction by multicellular tubers on proximal rhizoids.

Didymodon rigidulus

Didymodon umbrosus
Phenology Capsules maturity not determined.
Habitat Soil, lava, dolomite, cliff face, rock
Elevation moderate to high elevations (200-1900 m) (moderate to high elevations (700-6200 ft))
Distribution
North America; Mexico; s South America; Eurasia; n Africa
[WildflowerSearch map]
from FNA
CA; NM; NY; TX; Mexico; South America; Europe
Discussion

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 umbrosus is one of a number of mundivagant taxa whose distribution is associated with human activities (P. M. Eckel 1986). The proximal marginal cells are elongate and in distinctive rows. The transversely slit basal cells are distinctive in many specimens though also found in taxa of the Dicranaceae (R. H. Zander 1981b), some of which may belong in Pottiaceae (O. Werner et al. 2004).

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
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
Source FNA vol. 27, p. 543. FNA vol. 27, p. 547.
Parent taxa Pottiaceae > subfam. Barbuloideae > Didymodon Pottiaceae > subfam. Barbuloideae > Didymodon
Sibling taxa
D. anserinocapitatus, D. asperifolius, D. australasiae, D. bistratosus, D. brachyphyllus, D. eckeliae, D. fallax, D. ferrugineus, D. giganteus, D. johansenii, D. leskeoides, D. maschalogena, D. maximus, D. murrayae, D. nevadensis, D. nicholsonii, D. nigrescens, D. norrisii, D. perobtusus, D. revolutus, D. subandreaeoides, D. tectorum, D. tophaceus, D. umbrosus, D. vinealis
D. anserinocapitatus, D. asperifolius, D. australasiae, D. bistratosus, D. brachyphyllus, D. eckeliae, D. fallax, D. ferrugineus, D. giganteus, D. johansenii, D. leskeoides, D. maschalogena, D. maximus, D. murrayae, D. nevadensis, D. nicholsonii, D. nigrescens, D. norrisii, D. perobtusus, D. revolutus, D. rigidulus, D. subandreaeoides, D. tectorum, D. tophaceus, D. vinealis
Subordinate taxa
D. rigidulus var. ditrichoides, D. rigidulus var. gracilis, D. rigidulus var. icmadophilus, D. rigidulus var. rigidulus, D. rigidulus var. subulatus
Synonyms Barbula rigidula Barbula umbrosa, D. australasiae var. umbrosus, Trichostomopsis crispifolia, Trichostomopsis umbrosa
Name authority Hedwig: Sp. Musc. Frond., 104. 1801 (as rigidulum), (Müller Hal.) R. H. Zander: Phytologia 41: 22. (1978)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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