Images of British Lichens
Lecanora compallens Herk & Aptroot
Thallus a thin, grey crust, initially dotted with small, yellowish-green soralia and becoming uniformly powdery-sorediate, save for about a 1mm marginal zone, scratching whitish; apothecia unknown. This lichen is distinguished from the very similar and more common L. expallens by its lack of reaction with bleach, sodium hypochlorite (L. expallens giving a C+ deep yellow to red reaction). Widespread and probably locally frequent on bark of wayside and parkland deciduous trees, reported also on timber, but first recognised as a species in 1999 and distribution still poorly known.
Refs: Smith et al. (2009), 481; Dobson (2005), 217-218 (photo); Dobson (2011), 223 (photo); van Haluwyn et al. (2009), 150-1 (photo); van Herk & Aptroot (2004, 2013), 204-205 (photo); Wirth, Hauck & Schulz (2013), 1: 564 (photo), 565.
In addition to L. expallens, this species can be confused with Pyrrhospora quernea, which is more buff in colour, has somewhat coarser soredia and frequently has red-brown apothecia, and, like L. expallens, tests orange to red with bleach.
|On bark, Pembroke, Pembrokeshire, May 2009, det. P.A. Wolseley, upper photograph showing negative test with bleach|
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Uploaded June 2012, updated December 2013