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Images of British Lichens

Degelia atlantica (Degel.) P.Jørg. & P.James

Thallus blue-grey to lead grey, much paler brownish grey when dry, marked above with longitudinal marks and striations and with lobes concentrically undulate-ridged, giving the thallus a shell-like appearance, felted blue-black beneath and at the margins, isidia usually abundant, rounded, initially along the lobe margins and often forming extensive crusts across older parts of the thallus; apothecia rare. An Atlantic species of western Britain and Ireland, becoming locally frequent in north-west Scotland, on mossy trunks, especially on Hazel (Corylus avellana), and sometimes on mossy rocks and in sheltered crevices on seacliffs, a characteristic species of the 'Celtic Rainforest'.

Refs: Smith et al. (2009), 370; Purvis et al. (1992), 231; Dobson (2005), 160 (photo); Dobson (2011), 166-7 (photo); Whelan (2011), 90 (photo); Nordic Lichen Flora (2007) 3: 97, 177 (photo); Valcárcel et al. (2003), 178-9 (photo); Lichen Atlas of the British Isles 4: 1027 (1999).

D. cyanoloma, previously considered a variant of D. plumbea but recently restored to specific rank, resembles D. atlantica closely and occurs with it, but lacks isidia and is usually fertile with dark brown to blackish apothecia.


Degelia atlantica
In moist state, Glen Nant, Argyllshire, December, 2009
Degelia atlantica
Degelia atlantica
In dry state, on Hazel (Corylus avellana), Craighouse, Jura, May 2011 (BLS meeting)
Degelia atlantica
In dry state, on Hazel (Corylus avellana), Ardilistry, Islay, May 2011 (BLS meeting)

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Uploaded August 2011, last updated January 2016