Description: This epiphyte grows on the rough bark of oak, ash and sycamore and occasionally on old smooth bark. The green-brown to olive-black thallus produces numerous black spherical discs (perithecia) protected by a thick black involucrellum of cells. The perithecia contain six- to seven-septate spores. A section cut through the discs mounted in K shows the presence of purple pigments. In Ireland, the species is thinly scattered.

Key Identification Features:

• Epiphyte of old smooth bark and rough basic-barked trees; perithecia (0.2–0.5mm diam.) black with a thick involucrellum containing K+ purple pigments
• Spores six- to seven-septate.

Original text submitted by Vince J. Giavarini

Distribution Map from NBN: Porina borreri at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Porina borreri at iNaturalist World Species Observations database.