Images of British Lichens
Porpidia cinereoatra (Ach.) Hertel & Knoph
A crustose, 'lecideine' lichen with a white to grey, cracked thallus, black prothallus often visible in the cracks, soredia absent; apothecia black, pruinose when young. Widespread but mainly in the north and west, on base-poor rocks.
Refs: Smith et al. (2009), 742; Purvis et al. (1992), 495; Dobson (2005), 359 (photo); Dobson (2011), 362-3 (photo); Whelan (2011), 133 (photo); Wirth (1995), 2: 768; Valcárcel et al. (2003), 322-3 (photo); Puntillo (1996), plate 33 (photo).
Porpidia is part of the very large 'Lecidea group' of lichens – crustose species with dark or black apothecia which lack distinct 'thalline' margins, though they will usually have differentiated 'proper' margins the same colour as the disk. Microscopic examination of mature apothecia (and sadly they are often not mature) is usually necessary even to be sure of the genus, and field identification of all but a few distinctive species is risky. Dobson (2011), pp. 236-237, gives an invaluable analysis of the component genera.
|On siliceous, montane rocks, Beinn Airein, Isle of Muck, July 2012 (BLS meeting)|
|On upland boulder, Braemar, Aberdeenshire, April 2002|
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Uploaded July 2008, last updated August 2013 (first hosted at www-biol.paisley.ac.uk, January 2003)