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Images of British Lichens



Rhizocarpon geographicum (L.) DC.
 
'Map Lichen'


A well known and distinctive, yellow-green to bright yellow crustose lichen, the thallus cracking to produce angular areoles; apothecia flat, black, in microscopic section with an often K+ purple exciple, and with a brown to red-brown or greenish, K+ purple or green epithecium. 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); Valcárcel et al. (2003), 336-7 (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); Wirth, Hauck & Schulz (2013), 2: 985, 992 (photo); Moberg & Holmåson (1984), 131 (photo); Holien & Tønsberg (2008), 187 (photo); Stenroos et al. (2011), 408 (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).

Rhizocarpon geographicum
On evidently metalliferous, upland rockface, Langdon Common, Co. Durham, June 2009
 
Rhizocarpon geographicum
On stonework of old bridge, Kindrogan, Perthshire, March 2008
 
Rhizocarpon geographicum
Rhizocarpon geographicum
On coastal rocks, Kennedy's Pass, Ayrshire, May 2008


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Uploaded August 2008, last updated September 2013