pf339's picture

Millstone Grit Lichen

Observed: 28th August 2012 By: pf339
S159 Neighbourhood Nature - course complete
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Millstone grit lichen 1
Millstone grit lichen 2

Warty, light grey areolate crustose thallus. Dark prothallus just visible top left and along the top of the pictures. Large black lecideine apothecia (fingertip for scale). Some of the apothecia look lumpy and distorted. Growing on siliceous rock,millstone grit erratic, near limestone path. Possibly Porpidia macrocarpa.


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Some fungi are very poisonous so a mistaken ID could have serious consequences.

Species interactions

No interactions present.


JoC's picture

Porpidia spp

Alan Silverside says on his website, (see this for an example)
for all his Porpidia species entries, "Porpidia is part of the very large 'Lecidea group' of lichens – crustose species with dark or black apothecia which lack distinct 'thalline' margins, though they will usually have differentiated 'proper' margins the same colour as the disk. Microscopic examination of mature apothecia (and sadly they are often not mature) is usually necessary even to be sure of the genus, and field identification of all but a few distinctive species is risky. Dobson (2011), pp. 236-237, gives an invaluable analysis of the component genera."


AlanS's picture


Saves me typing it again here.

I don't think it is Porpidia macrocarpa as it has pruinose apothecia. P. platycarpoides is more likely, but I won't name these unless I have the specimen in hand and can do the microscope work.


pf339's picture

Millstone Grit Lichen

Thank you for the two comments with the references and information about possible identification (but for a likely identity microscope work still needed).