Caloplaca flavovirescens

C. flavovirescens is a very common lichen over much of North America where it may be found on limestone and other calcium rich rocks, as well as, manmade concrete structures. In Subtropical Florida, it is very common on any unpainted concrete, including sidewalks. Although the basement rock of South Florida is totally limestone, it is strange we have never found this lichen associated with this natural substrate. At a young stage, the thallus becomes cracked. The cracks widen until the surface becomes little islands of thalline and/or apothecial pieces.