Family: Trypetheliaceae Species: Arthopyrenia platypyrenia Growth type crustose Photos: On Weigela twig. Co. Cork, SW Ireland. Identification confirmed by John Douglass The very inconspicuous non-lichenised thallus has tiny (0.25 - 0.45mm), +/- rounded perithecia which form below an involucrellum. The asci are (4-)8 spored, spores 3-4(-7) septate, (19.5-) 23-27.5 x 8-11 µm. Micrograph below. Chemical reactions negative Occurs on bark, especially of Hedera. Similar: Arthopyrenia subcerasi only occurs on Betula and has persistently 3-septate spores

Microscope photograph

Arthopyrenia platypyrenia . May 2012