Rhizocarpon tetramerum
- Innhold
- Morphology
- Chemistry
- Habitat
- Comment
Morphology
Thallus areolate, up to 5 cm diam.; hypothallus thin, black; areolae up to 0.3 mm diam., pale grey to brownish grey or ochraceous, dull, orbicular to angular, plane to moderately convex; medulla KI–. – Apothecia up to 0.3 mm diam., black, epruinose, orbicular, plane to moderately convex, with a persistent or disappearing margin; excipulum greenish black in the rim, paler green to colourless in inner part, containing crystals dissolving in K, K– (crystals K+ yellow; pigment turning more brightly green); hypothecium medium brown, K–; hymenium colourless, containing crystals dissolving in K; epihymenium olivaceous green, K– (crystals K+ yellow, pigment turning more brightly green); ascospores 8 per ascus, 3-septate to submuriform, persistently colourless, 15–20 × 6–9 µm. – Conidiomata not seen.
Chemistry
Stictic acid; spot tests: medulla PD+ orange, K+ yellow, C–.
Habitat
On siliceous rock in the lowlands.
Comment
Poorly understood species. In Norway known from a single locality.