Aspicilia caesiocinerea (images of British lichens)

Thallus a warted, blueish- or brownish-grey crust; apothecia more or less immersed, with thick, thalline margins and black, sunken discs. Widespread and locally frequent on base-poor rocks. Distinguished from members of the A. cinerea group by chemical tests (Pd-, K-).
Refs: Smith et al. (2009), 183; Purvis et al. (1992), 98; Dobson (2005), 72-3 (photo); van Herk & Aptroot (2004), 64-65 (photo); Moberg & Holmåson (1984), 111 (photo, upper left); Hansen & Anderson (1995), 77 (photo); Thomson (1997), 63, 65 (photo).

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