Pertusaria leioplaca (images of British lichens)

Thallus a thin, more or less smooth to somewhat warted, grey-cream to pale green crust, surface with larger, isolated, flat-topped warts, these maturing to contain usually single apothecia with visible rims and deeply sunken discs; asci mostly 4-spored. Widespread and often common, more so in the north and west, on smooth-barked trees in sheltered situations.

Refs: Smith et al. (2009), 683; Purvis et al. (1992), 456; Dobson (2005), 327-8 (photo); Dobson (2011), 328 (photo); van Haluwyn et al. (2009), 184-5 (photo); van Herk & Aptroot (2004), 290-1 (photo); Wirth (1995), 2: 698 (photo); Wirth et al. (2004), 280 (photo).

lastdragon.org

Images of British Lichens