Description: This rare lichen is one for the purist and really tests the calibre of the budding lichenologist. The thallus has little to distinguish it and is scarcely visible. The discs resemble those of A. punctiformis (described elsewhere) although not immarginate as in that species, but have a well-developed margin and a slightly flexed surface. It is an oceanic, smooth-bark species growing mostly on hazel. The spores are colourless and one-septate; this separates it from Melaspilea species. In Ireland, it is currently known from County Cork but there are older records from Counties Kerry and Galway.

Key Identification Features:

• Very like A. punctiformis but the discs have a well-developed margin and a flexed or twisted surface; it has an oceanic distribution growing on smooth bark or the flat, raised ribs of fissured bark in western woodlands
• Spores colourless, one-septate (three-septate in A. punctiformis).

Original text submitted by Vince J. Giavarini

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

iNaturalist: Arthonia excipienda at iNaturalist World Species Observations database.