Species: Lecanora campestris
Photos: On stone walls and concrete post. Co. Cork, SW Ireland.
Greyish-white, warted or areolate thallus usually with fimbriate white prothallus. Large chestnut to dark-brownish apothecia are crowded in centre of thallus. Smooth margins, contorted with age. Asci 8-spored, the spores simple, 10-14(-17) x 6-8.5(-9) Ám. Microscope photograph below.
K+ yellow, C-, P- or P+ very pale yellow, UV- or UV+ dull orange
Frequent on basic to calcareous stone and walls, also found on nutrient-enriched acidic rocks and wood.
Similar: Lecanora horiza has a darker grey, K- thallus