Description: The yellow-grey thallus with a rather dark and sooty cast that often distinguishes this species in the field from its Irish relatives has a peculiar feature which tells it outright on close inspection: the spherical discs or perithecia have their spore-exit points or ostioles laterally positioned instead of at the apex of the disc. A section through the disc in potassium hydroxide solution (K) shows no reddening of the tissues and an absence of oil droplets which are easily visible under the microscope. Spores are three-septate and about 20–25µm long. Smooth bark in the vicinity of old woodlands. In Ireland, records are few: County Clare and County Kerry.

Key Identification Features:

• Discs (perithecial) skewed with terminal opening (ostiole) laterally positioned or well off-centre
• Disc tissues unchanged in K without oil droplets; no lichen substances detected.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Pyrenula acutispora at iNaturalist World Species Observations database.