Description: Formerly recorded as B. efflorescens (a taxon which is now known to have a more eastern distribution in Britain and Ireland) the thallus of this species has pale green or yellowish soralia which react Pd+ orange-red. The species is frequently sterile. When fertile it can be separated from B. efflorescens by the blue-grey colouration of the discs which, when squashed under a microscope slide, are seen to contain a blue-green pigment. There is one collection from County Fermanagh where material was gathered from a willow. The habitat of both B. britannica and B. efflorescens is identical: mossy tree bark of deciduous trees in old woodland.

Key Identification Features:

• Pale green or yellowish soralia on mossy tree bark, testing Pd+ orange-red; discs when present, blue-grey (not beige to red-brown = B. efflorescens)
• Disc in squash contains a blue-green pigment.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Biatora britannica at iNaturalist World Species Observations database.