Description: This rather elegant foliose lichen of tree branches in undisturbed woodland or entangled among Calluna in valleys near the coast is closest in appearance to P. perlatum but differs in chemistry, and in the black marginal cilia which can be up to 5mm long (compared with 1–2mm long in P. perlatum). Lobes are loosely attached and the medulla is KC+ red (KC + yellow-orange in P. perlatum). In Ireland, the species is uncommon and has a predominantly west coast distribution.

Key Identification Features:

• Thallus more loosely attached than P. perlatum and with long, black marginal cilia
• The medulla tests KC+ pink or red.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Parmotrema arnoldii at iNaturalist World Species Observations database.