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Images of British Lichens

Caloplaca aractina (Fr.) Häyrén

Thallus dark blue-grey to ± black, somewhat lumpy-areolate or cracked but surface smooth, with a slight oily appearance and lacking isidia or blastidia; apothecia with brownish-orange, minutely roughened discs and thick, dark grey, thalline margins; the whole lichen closely resembling the widespread C. chlorina, but lacking isidiate blastidia and differing somewhat microscopically. A very rare species of coastal rocks, on the Lizard Peninsula in Cornwall, recently found in N.Wales, uncertain elsewhere.
British Red Data Book species: critically endangered (but this assessment now outdated).

Refs: Smith et al. (2009), 253; Purvis et al. (1992), 146; Lichen Atlas of the British Isles 6: 234 (2001).

In recent years, C. aractina has been treated as confined in Britain to the Lizard Peninsula, where a number of sites are now known. In the Lichen Atlas of the British Isles, other west-coast records, as in Purvis et al. (op.cit.), are considered to have referred to C. ceracea. However, C. aractina has recently been found and authenticated at now two coastal sites in N. Wales (, opening up the possibility that this rare species awaits discovery (or re-discovery?) elsewhere.


Caloplaca aractina
Caloplaca aractina
Caloplaca aractina, close view
Caloplaca aractina, close view
On boulders above shore, near Coverack (Lizard Peninsula), Cornwall, June 2013

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© A.J. Silverside
Uploaded October 2013, updated January 2016