Buellia aethalea forme K- sur substrats artificiels.

   This form colonizes artificial substrates by the sea (here a plastic boat wreck). It differs from Buellia aethalea forme K+ rouge sur substrats artificiels only by its colored chemical reactions: K-, KC-, C-, P-. Beware of Rhizocarpon reductum whose apothecia are lecideins but which does not seem to grow in polluted environments.