Arthonia varians (Davies) Nyl.

Parasite lichen of Lecanora rupicola apothecia.

      Thallus absent and only apothecia developing in the hymenium of the host apothecia in the form of black spots 0.3-1 mm in diameter of irregular shape and occupying a more or less large place in the apothecia of the host (but rarely all of them). They develop at the same level as the hymenium of the apothecia of the host and rarely a little in relief. Utriform asci with 8 spores. Spores ovoid to oblong, sometimes somewhat clavate, smooth and colorless, (1) 2-3 septate, 11-17 x 5-6.5 µm according to literature; 13-15 x (5) 6-7 µm according to our measurements. Branching paraphyses with apex stuck with ill-defined dark matter. Common on the apothecia of Lecanora rupicola s.l., particularly in the aerohaline zone.

N.B. Species fairly similar to Arthonia apotheciorum which grows on the apothecia of the Lecanora dispersa group.