A lichen of dry bark on veteran Oaks with a sub-oceanic distribution in Europe. It has an extensive whitish thallus with scattered black urceolate pycnidia, the white pruinose walls giving the impression of a neat white cuff-like thalline rim to the pycnidia. The apothecia have not yet been observed in Britain, but are distinctive, adnate and lacking a margin, with a densely white-pruinose disc. All parts K−, C−, KC−, Pd−.
Appears very rare in Britain with single sites known in England (Shropshire) and Wales (Cardiganshire), but potentially overlooked as sterile Lecanactis abietina, which occurs in the same habitat, but this has C+ red pycnidia, which are also much less fluffy. This lichen should be looked for elsewhere on veteran Oaks in the less oceanic parts of the country.
See ITALIC 6.0, Atlas of Czech Lichens and Frisch et al (2015) The Lichenologist. 47: 233 - 256.
Cannon, P., Ertz, D., Frisch, A., Aptroot, A., Chambers, S., Coppins, B. J., Sanderson, N. A., Simkin, J. & Wolseley, P. (2020) Revisions of British and Irish Lichens Volume 1 August 2020 Arthoniales: Arthoniaceae. BLS Link