This fungus causes a fuzzy, brown coating on slightly, or very, bleached areas of the thallus and apothecia of Xanthoria parietina. Spores are formed around the tips of specialised hyphae. The spores break away to leave distinct scars that give the tips of these hyphae a knobbly appearance. Spores are variable but generally ellipsoid with 1-4 cells.
Similar species: Two other fungi produce coloured layers on Xanthoria parietina but only on the apothecia. Cladosporium licheniphilum produces a brown, spiky layer. Its spores are produced on hyphae that are thick-walled and have lots of cross walls. Xanthoriicola physciae causes a black sooty surface.
Also see Fungi of Great Britain and Ireland
On the thallus and apothecia of Xanthoria parietina in nitrogen-rich lichen communities.
Very few records in the UK but probably overlooked.
Text by Fay Newbery