Images of British Lichens
Caloplaca flavovirescens (Wulfen) Dalla Torre & Sarnth.
Thallus pale yellow or sometimes slightly greyish or greenish, cracked-areolate with uneven surface; apothecia deeper in colour, bright orange to deep orange-brown, dispersed to crowded, 0.3–1.3mm diam. (from Wilk, 2012), flat, becoming somewhat convex, proper margin paler, remaining visible long into maturity, thalline margin poorly developed but sometimes persisting as an inconspicuous, thin, unevenly and minutely crenulate rim, ascospores 10.0–20.5 x 6–12µm with septum 3.5–10µm wide (Wilk, op. cit.). Widespread and locally common on calcareous rocks, walls (especially with downwash from mortar), concrete and on coastal rocks.
Refs: Wilk (2012), 24 (photo), 67-9; Smith et al. (2009), 263; Purvis et al. (1992), 152; Dobson (2005), 102, 103 (photo, atypical); Dobson (2011), 111-12 (photo, atypical, poorly printed); Wirth (1995), 1: 218 (photo), 219; Wirth, Hauck & Schulz (2013), 1: 289, 301 (photo); van Herk & Aptroot (2004, 2013), 96-7 (photo); Brodo et al. (2001), 201 (photo); Walewski (2007), 58 (photo), Lichen Atlas of the British Isles 6: 255 (2001).
C. flavovirescens is often a distinctive and attractive species, and can be confirmed microscopically by the large spores with the septum sometimes up to half the length of the spore. C. crenulatella is a somewhat similar but smaller species with much smaller apothecia and with ascospores with narrow septa. C. dalmatica has a smoother, more continuous, often snail-grazed thallus, usually dissected by fine, black cracks, and smaller ascospores. C. flavorubescens is similar in appearance as well as in name, but is a now very rare species on naturally nutrient-rich tree bark.
|On coastal rocks, Turnberry, Ayrshire, June 2011|
|On wall, Saltash, Cornwall, August 2008|
|On wall above loch shore, Rowardennan (Loch Lomond), Stirlingshire, May 2010|
|On stonework of old bridge, Glen Tilt, Perthshire, April 2008 (det. John Douglass)|
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Uploaded October 2013, last updated January 2016