Opegrapha
Crustose lichens or lichen parasites, containing trentepohliate algae, or algae lacking; thallus smooth, cracked, areolate or sorediate; apothecia lirellate, often asterisk-like or snaking, the disc slit-like or gaping, often pruinose; rim black, formed of shortly cylindrical cells densely matted with dark brown pigment masses, usually continuous under the hymenium; hymenium formed of densely branched and anastomosing hyphae embedded in gel, often dark-pigmented in upper portions; hypothecium colourless, thin; asci cylindric to elliptical or broadly clavate, with a moderately thickened, IKI+ light bluish tholus having an ocular chamber over which is an IKI+ darker blue ring structure that appears as two dashes; spores 8 per ascus, colourless, fusiform, oblong, elliptic, or acicular, 1-15 septate, often surrounded by a thick gelatinous perispore.
References: Purvis et al. 1992; Ertz & Egea 2007.
| 1a. | Spores usually with more than 3 septae, 19-33 × 5-6 µ; thallus grey and inconspicuous; uncommon …Opegrapha varia |
| 1b. | Spores consistently 3-septate, 18-28 × 5-8 µ; thallus comparatively conspicuous, whitish; rare …Opegrapha herbarum |
Opegrapha herbarum Mont.
Thallus thin, matte, pale brownish grey or whitish, sometimes immersed; apothecia simple or a few with a single branch, 0.5-2.5 × 0.2-0.3 mm, jet black, rarely greenish pruinose, the disc slit-like or sometimes gaping, the rim dark brown throughout; hymenium 60-90 µ high, colourless, I+ reddish, upper portions brown or reddish brown; hypothecium pale brown; spores elliptical to elliptic-fusiform, 18-28 × 5-8 µ, consistently 3-septate, sometimes turning brownish with age, with a gelatinous perispore 0.5-1.5 µ thick.
Reactions: All spot tests negative.
Contents: No known lichen substances.
Habitat: On bark of Populus trichocarpa and Thuja along rivers. Lower elevations.
Similar Species: Arthonia excipienda appears similar, but has smaller apothecia and 1-septate spores. Arthonia dispersa lacks an apothecial rim. Opegrapha varia is very similar, but can usually be distinguished in the field by its darker, less conspicuous thallus.
Specimens: Björk 12230.
Local Status: Rare.
Opegrapha varia Pers.
Thallus medium olive-gray, thin, matte, inconspicuous; apothecia 0.2-2.5 × 0.2-0.5 mm, jet black, simple or a few with a single branch, the disc slit like or, more often, gaping, the rim thick and persistent, the rim interior dark brown throughout; hymenium 60-80 µ high, colourless, I+ red, light to medium brown in upper portions; spores usually with more than 3 septae, 19-33 × 5-6 µ.
Reactions: Spot tests all negative.
Contents: No known lichen substances.
Habitat: On bark of Populus trichocarpa and Thuja along rivers and lakes. Lower elevations.
Similar Species: Arthonia excipienda appears similar, but has smaller apothecia and 1-septate spores. Arthonia dispersa lacks an apothecial rim. Opegrapha herbarum is very similar, but can usually be distinguished in the field by its whitish or pale grey, more conspicuous thallus.
Specimens: Björk 9891, 12231.
Local Status: Uncommon.