Description: In the field, this species can usually be distinguished by its yellow-orange immersed thallus pierced by conspicuous shiny black, spherical discs (perithecia). The disc ostiole (opening) is centrally positioned. Under the microscope, minute oil droplets are present in the hymenium. In Ireland, it occurs in the oceanic woodlands of the far north and west.

Key Identification Features:

• Thallus yellow-orange with conspicuous perithecia with a central ostiole
• Section through disc in K shows up some reddish pigments; tiny oil droplets in the hymenium between and around the spore sacs (asci).

Original text submitted by Vince J. Giavarini

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

iNaturalist: Pyrenula occidentalis at iNaturalist World Species Observations database.