Description: This crustose epiphyte is comprised of small, squat, white to grey-green, multi-finger-like squamules (<3 mm long). It grows only on trees (such as oak) where there is known to be a long history of woodland continuity. The smooth, conical to barrel-shaped discs are not uncommon, though through a lens it is the strange squamules which first alert the observer. It has eight spores per spore sac (ascus) and is confined more or less exclusively to south-west Ireland but should be searched for in all known ‘ancient’ woodland.

Key Identification Features:

• On very old trees in old woodlands; squamules green, never brown-tinged
• Agonimia tristicula is similar and may also occur on trees but has bronze-tinted squamules and only one or two spores per ascus.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Agonimia octospora at iNaturalist World Species Observations database.