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Images of British Lichens

Caloplaca saxicola (Hoffm.) Nordin
(includes C. pusilla (A.Massal.) Zahlbr.)

Thallus yellow to pale, brownish orange, placodioid (i.e. a crust but lobulate at the margins), lobules pruinose, appearing almost scabrid-pruinose under a lens; apothecia orange to orange-brown, crowded in the centre of the thallus. Widespread, generally common but less so in the west, on cement, concrete and calcareous rocks, walls and monuments.

Refs: Gaya (2009), 86, 185 (photo, C.  saxicola, ss.), 73, 181 (photo, C. pusilla); Wilk (2012), 10 (photo, C. pusilla), 21 (photos, C. pusilla & C. saxicola), 51-2 (C. pusilla), 52-3 (C. saxicola); Smith et al. (2009), 270; Purvis et al. (1992), 157; Dobson (2005), 106-7 (photo); Dobson (2011), 115-6 (photo); Whelan (2011), 62 (photo); Wirth (1995), 1: 217, 237 (photo); Wirth et al. (2004), 236 (photo); Wirth, Hauck & Schulz (2013), 1: 285, 309 (photo, C. pusilla); Moberg & Holmåson (1984), 187 (photo); Stenroos et al. (2011), 88 (photo); van Herk & Aptroot (2004, 2013), 104-106 (photo); Thomson (1997), 168; McCune & Geiser (2009), 48 (photo); Lichen Atlas of the British Isles 6: 277 (2001).

Gaya (2009) separates C. pusilla as a separate species, differing in being distinctly lobed at the thallus margin, with lobes pruinose, whereas C. saxicola is regarded as a rarer taxon with margins scarcely lobed, and with the surface perhaps thinly crystalline but not pruinose. On this basis, the common British taxon is C. pusilla. I have photographed and collected what I consider to be "true" C. saxicola (as interpreted in Europe), pending microscopic confirmation, and expect to split this page sometime in the future.

FGBI: (evidently includes C. pusilla)

Caloplaca saxicola
Caloplaca saxicola
Caloplaca saxicola
On rockface in old limestone quarry, Tomintoul, Banffshire, August 2009  [matches C. pusilla var. pusilla]
Caloplaca saxicola
On concrete esplanade wall, Arbroath, Angus, April 2002  [may match C. pusilla var. pulvinata]

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© A.J. Silverside
Uploaded March 2008, last updated January 2016 (first hosted at, January 2003)