Rhizocarpon expallescens
- Innhold
- Morphology
- Chemistry
- Habitat
- Comment
- Look-alikes
Morphology
Thallus rimose to areolate, up to 5 cm diam.; hypothallus usually distinct, black; areolae up to 0.5 mm diam., greyish white to medium grey, dull, contiguous or scattered, more or less angular, plane; medulla KI–. – Apothecia up to 1 mm diam., black, epruinose, orbicular, remaining more or less plane or becoming moderately convex, narrowly marginate; excipulum brownish black in the rim, inner part paler brown, K–; hypothecium brown, K–; hymenium colourless; epihymenium bright green to greenish black, K–; paraphyses with a sharply delimited, green pigment cap in the apical cell; no crystals or granules in the apothecia; ascospores 8 per ascus, 1-septate, persistently colourless, 14–17 × 6-9 µm. – Conidiomata not seen.
Chemistry
No lichen substances.
Habitat
On crystalline schist.
Comment
The species is rarely collected. It is morphologically similar to R. caeruleoalbum and differs mainly in the absence of stictic acid.
