Rhizocarpon geographicum (images of British lichens)

A well known and distinctive, yellow-green to bright yellow crustose lichen, the thallus cracking to produce angular areoles; apothecia flat, black. Widespread and, in the north and west, often very common and conspicuous on exposed, base-poor rocks. Variable; the photographs show subsp. geographicum.

Refs: Smith et al. (2009), 800; Purvis et al. (1992), 537; Dobson (2005), 386 (photo); Dobson (2011), 390 (photo); Allen (2007), 11 (photo); Jahns (1983), 208-9 (photo); Whelan (2011), 139 (photo); Wirth (1995), 1: 403 (photo, yellow lichen in mosaic with Fuscidia kochiana), 2: 805; Wirth et al. (2004), 203 (photo, yellow, with Fuscidia kochiana); Moberg & Holmåson (1984), 131 (photo); Holien & Tønsberg (2008), 187 (photo); Hansen & Anderson (1995), 112 (photo); Pope (2005), 54 (photo); Øvstedal & Lewis Smith (2001), 299, plate 74 (photo); Brodo et al. (2001), 635 (photo); Thomson (1997), 536; Walewski (2007), 66 (photo).

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Images of British Lichens