Acarospora umbilicata f. congredians

An Acarospora with densely pruinose areoles. On siliceous rocks subjected to seepage from adjacent calcareous rocks or mortar, particularly on old walls; very local. The status of this species requires further study. Much named British material has proved to be pruinose morphs of A. fuscata which has flat areolae and irregular but not pseudo-gyrose discs immersed in areoles.