Arthonia apotheciorum (A. Massal.) Almq.

Lichen parasitizing the apothecia of lichens of the genus Polyozozia (Lecanora, Myriolecis) albescens.

    No thallus. Apothecia develop within the host's apothecia, initially as small, rounded black spots 0.1-0.3 mm in diameter. These spots then increase in size, or coalesce if there are several, to invade the entire surface of the host's apothecia, which becomes entirely black. Clavate asci measure 60-70 x 10-15 µm according to our measurements. Spores are elliptical to clavate, 1-septate, 9-15 x 3-5 µm according to the literature, 10-13 x 3-4 µm according to our measurements. No characteristic chemical color reactions. This species parasitizes the apothecia of the Polyozozia albescens group.

_ Appearance little different from Arthonia varians which comes from Glaucomaria (Lecanora) rupicola and which has narrower spores.