Description: This crustose epiphyte is virtually identical to E. avellanae but is the commoner of the two species in Ireland. The immersed thallus may be sprinkled with minute spherical discs (perithecia) or ‘bark-pimples’ and in this respect, it is very similar to species of Arthopyrenia and easily mistaken for them. On hazel bark, minute swellings occur that are clearly not discs. These are the pycnidia (you will need to scan the bark in some detail to find them) which, under the microscope, are seen to contain magnificent spore-like structures called macroconidia (14-19 x 6-7µm) which are three-septate with rounded cavities called locules. If you are a lichen twitcher you would probably relish finding this species, but it is easily collected inadvertently in the field by beginners, in which case it is then counted as an ‘extra’ by a lichen referee to whom unidentifiable scraps of this nature could be sent (along with grid reference, site name, date of collection, collector’s name and host tree). Look for it in old hazel woods. It has been recorded only from the northern half of Ireland.

Key Identification Features:

• Grows on hazel; thallus immersed, often pycnidia are present represented as minute, faint swellings just below the bark
• Macroconidia are three-septate — see the above sizes which are larger than in E. avellanae, hence ‘grandicula’.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Eopyrenula grandicula at iNaturalist World Species Observations database.