Lecanora ochroidea

Thallus continuous and finely cracked to areolate, clearly delimited, areoles often uneven in height, ± flat, margins crenulate, white or pale grey, surface coarsely granular to warted; prothallus white, fibrous, generally well-developed. Apothecia 0.7–2 mm diam., scattered or aggregated, sessile and finally constricted below; thalline margin entire, tending to be paler than the thallus, becoming excluded; disc pink- to pale grey-brown, convex to almost subglobose, usually densely white-pruinose; epithecium brown, granular, K+ red (with needle-like crystals); hymenium 60–80 (–100) µm tall; paraphyses 1.5–2 µm diam., unbranched or sparsely branched, especially above, apices to 3.5 µm diam., generally with the terminal cell subglobose. Ascospores (8–) 10–14 × (5–) 6–8.5 µm. Thallus C–, K+ yellow→red, Pd+ orange to red, UV± pale orange (atranorin, chloratranorin, protocetraric, norstictic and connorstictic acids).

Lecanora ochroidea was confused with L. subcarnea but is distinguished by its K+ yellow→red reaction (norstictic acid) and its pale UV fluorescence. L. subcarnea is largely confined to inland upland rocks, but L. ochroidea has been found inland in oceanic woodland in Ireland and habitat should not be taken as a guide, especially in more oceanic areas. Glaucomaria rupicola also has white pruinose discs that are C+ yellow, immersed and flat, and grows in exposed situations.