Order: Arthoniales Family: Arthoniaceae
Species: Arthonia didyma
Photos: Glengarriff woods, Co. Cork, SW Ireland.
Identification needs confirming
Immmersed thallus with small, flat, brown or black apothecia. Spores are 1-septate, 14-17 x 4.5-7 Ám, colourless becoming brown. Pycnidia rare. Microscope photograph below.
Chemical results: Red-brown pigment K+ grey or olive. Epithecium, hymenium and sometimes the hypothecium with orange-red K+ purple-violet pigment
Found on the smooth bark of shrubs and trees (usually Corylus) in unpolluted woodlands