Description: This minute, crustose lichen falls into the ‘bark pimple’ category. It is faithful to oak but may also grow on hazel and should be searched for only on twigs and small diameter branches. The thallus is easily overlooked as a bark stain upon which the tiny spherical discs (perithecia) are clustered together into tight groups of three to five. A squash under the microscope will show the spores (12-18 X 5-7&

371;m) to have a submuriform structure rather like a small church window divided into ‘lights’. All areas except central and south-east Ireland.

Key Identification Features:

• Stain on bark with clusters of three to five minute perithecia
• Always on twigs or narrow branches (oak and hazel), the spores submuriform.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Cyrtidula quercus at iNaturalist World Species Observations database.