Order: Lecanorales Family: Physciaceae
Species: Buellia disciformisGrowth type crustose.
Photos: On Ash. Co. Cork, SW Ireland. Left identified by Andy Acton
Thallus thin and smooth to thick and cracked, whitish to pale yellow-grey, often with black prothallus. Apothecia with flat to slightly convex black discs, the margins usually persistent. Asci 8-spored, spores brown, 1-septate, 17-26 x 7-10 Ám. Micro photo below.
Thallus K+ clear yellow, C-, P+/- yellow, UV-
Can be frequent on twigs, branches and trunks of smooth-barked trees. Mainly found in west and north of Ireland.
Similar: Lecidella elaeochroma. Usually C+ orange, simple spores Diplotomma pharcidium can appear similar but is very rare. Spores 3-septate to sub-muriform