Rhizocarpon ridescens
- Innhold
- Morphology
- Chemistry
- Habitat
- Comment
Morphology
Thallus areolate, up to 10 cm diam.; hypothallus well developed, black; areolae up to 1 mm diam., bright yellow, dull, mostly scattered, thick, more or less orbicular, moderately convex to hemispherical, smooth, sorediate; medulla KI+ dark violet. – Apothecia not common, up to 1 mm diam., black, epruinose, more or less orbicular, plane, persistently marginate; excipulum brownish black in the rim, paler in inner part, K+ red; hypothecium dark brown, K–; hymenium colourless or pale brown; epihymenium dark reddish brown, K+ red; no crystals or granules in the apothecia; ascospores poorly developed, up to 8 per ascus, submuriform, dark brown, 20–30 × 12–16 µm. – Conidiomata not seen.
Chemistry
Rhizocarpic and psoromic acid; spot tests: medulla PD+ yellow, K–, C–.
Habitat
Growing on sun-exposed, siliceous rocks that are usually rich in iron minerals, both in the lowlands and in the mountains. Rare.
Comment
The only yellow, sorediate species in the genus in Norway.