Dirina massiliensis (images of British lichens)

Thallus variable, typically rounded with a delimited and sometimes zoned margin, thin and diffuse to thick, with convex areoles, brownish grey to chalky white, scratching orange (Trentepohlia photobiont), sorediate in f. sorediata, the soralia grey to grey-brown, initially delimited but coalescing in the centre of the thallus; apothecia present only in f. massiliensis, grey, pruinose. Widespread, especially on basic rocks, but evidently more common in the south-east, developing the thick, chalk-like thallus on hard limestones (Smith et al., 2009). The f. massiliensis is much rarer and said to occur mainly on vertical faces of hard limestones near the coast.

Refs: Smith et al. (2009), 383; Purvis et al. (1992), 239; Dobson (2005), 168-9 (photo, both forms); Dobson (2011), 174 (photo, both forms); van Herk & Aptroot (2004), 176-177 (photo, f. sorediata, as species); Wirth (1995), 1: 381 (photo, f. sorediata, limestone variant, as D. stenhammari); Puntillo (1996), plates 16,17 (photos, incl. f. sorediata).

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Images of British Lichens