Description: This uncommon lichen with spherical discs (perithecia) grows on damp siliceous rocks by loughs and upland rivers. The thallus is thin, smooth, and green-brown to purple-grey, and it is this violet hint to the colouration that should alert the lichen hunter. The black perithecia are between one-quarter to one-half immersed often forming tight constellations. The perithecia are covered by a hard outer layer (involucrellum) that is purple-violet to purple-brown in a squash. The six-seven-septate spores are large: 32-45 x 5-6&

371;m but lack longitudinal divisions (like mullions on a stained-glass window). South-west Ireland.

Key Identification Features:

• Thallus often with violaceous or purple tinge; clustered perithecia up to half immersed and large spores (six-nine-septate)
• On damp, granitic rocks: stream gorges, outcrops by lough edges; differs from the var. lucens in spores lacking longitudinal divisions.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Porina guentheri at iNaturalist World Species Observations database.