Scan of specimen, Thalline margin with Pd + yellow reaction on far left centre
The thallus is greyish-white and verrucose, with white low mounds of delimited white soralia and is K + yellow, Pd+/– faint yellow, while there is a stronger reaction Pd + yellow reaction on the thalline margin. The thalline margin has large crystals but I did not find any spores. I will have a go again tomorrow.
Closer scan of thallus
Apothecia with pruina under microscope
There is a useful paper in the Lichenologist on European sorediate Lecanora s. lat. Malíček et al (2017) "Corticolous sorediate Lecanora species (Lecanoraceae, Ascomycota) containing atranorin in Europe" https://doi.org/10.1017/S002428291700038X or https://www.researchgate.net/publicatio ... _in_Europe. In this the lichen keys out as Lecanora variolascens. This is closely related to Lecanora barkmaniana and differs in the strongly pruinose disk and smaller spores in Lecanora variolascens. The pictures of Lecanora variolascens look very like mine. There are also accounts at https://www.afl-lichenologie.fr/Photos_ ... ascens.htm and http://italic.units.it/index.php?proced ... e&num=1271
Malíček et al (2017) give the habitat as
Which also matches the Oak branch it was on. It appears to be rare and very infrequently recorded. Looks promising, I will just see if I can find spores tomorrow.Occurs on ±acidic bark (mainly of oaks and pines) but usually in slightly eutrophicated places