Hi,
I found this lichen on an Elder twig and it keyed out to Bacidia arceutina, but I just wanted to check I haven’t gone wrong somewhere. All tests negative – K-, C-, Pd-, UV-
The apothecia only had yellow/brown pigments in the epithecium and hypothecium, which faded to just yellow in K (photos below). There were no purple or green pigments.
The spores were in the range 35-55X1.2-2.5 um and were 3 to 7 septate.
The hymenium was I+ blue.
Thanks,
Sylvia