Order: Teloschistales       Family: Teloschistaceae Species: Xanthoria parietina Growth 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 µm. Microscope photograph below. Host to many lichenicolous fungi including Xanthoriicola physciae, Arthonia parietinaria and Illosporiopsis christiansenii 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: Xanthoria calcicola, X. polycarpa and X. aureola

Microscope photograph

Xanthoria parietina.