LICHALP

Placynthium caesium (Fr.) Jatta

Syn.: Bacidia caesitia (Nyl.) Jatta, Collolechia caesia (Fr.) A. Massal., Lecidea caesitia Nyl., Lecidea contigua (Hoffm.) Fr. var. caesia Fr., Lecidea triptophylla Ach. var. caesia Schaer., Pannaria nigra (Huds.) Nyl. var. caesia (Fr.) Malbr., Placynthium caesitium (Nyl.) Hue, Placynthium garovaglii (A. Massal.) Malme var. subtile G. Czeika, Scoliciosporum caesitium (Nyl.) Jatta

Lichenised.

Substrate: calciferous rocks

Altitudinal range: from the submediterranean/colline belt (potential vegetation: mixed deciduous forests dominated by Quercus and Carpinus) to the subalpine belt (potential vegetation: open, taiga-like forests dominated by Larix decidua and/or Pinus cembra and Rhododendron)

Note: a species with a partly unusual set of characters (but generic arrangement recently confirmed by molecular data), with a crustose thallus lacking a prothallus, black biatorine apothecia, and 3-6-septate, fusiform ascospores; a mainly southern species in Europe, found on steeply inclined surfaces of calcareous rocks with some water seepage after rain. In Northern Europe it has been frequently confused with P. garovaglii, which is a completely different species, although material with poorly developed marginal lobes may be difficult to identify.