Pertusaria albescens (images of British lichens)

Thallus pale greenish grey to grey, often zoned at the margin, surface with often abundant, often (but not always) clearly delimited, round soralia that lack a bitter taste (compare with P. amara); apothecia rare. Widespread on bark of deciduous trees, rarely on other substrates.

Refs: Smith et al. (2009), 676; Purvis et al. (1992), 450; Dobson (2005), 322 (photo); Dobson (2011), 323 (photo); Whelan (2011), 127 (photo); van Haluwyn et al. (2009), 162-3 (photo); van Herk & Aptroot (2004), 286-7 (photo); Wirth (1995), 2: 695 (photo), 697; Wirth et al. (2004), 298 (photo); Frahm et al. (2010), 85 (photo).

lastdragon.org

Images of British Lichens