Species: Xanthoria parietinaGrowth type foliose.
Yellow-orange thallus with large lobes, greyish-yellow in shade. Lobules sometimes present in centre of thallus. Abundant apothecia, discs with smooth margins. Ascus 8-spored, the spores colourless and polaricular, 12-16 x 7-9 Ám. Microscope photographs below.
Host to lichenicolous fungi including Xanthoriicola physciae and Arthonia molendoi
Common on nutrient-rich rocks, trees, walls and roofs throughout Ireland. Coastal in 'orange' and 'grey' zones, also occurs inland in both rural and urban habitats. Very resistant to air pollution and increasing rapidly due to nitrates and ammonia from car exhausts and agricultural chemicals. K+ crimson / purple.
Similar: X. calcicola, X. polycarpa and X. ectaneoides / aureola