Cladonia sp

Is it time to have another look at the “what is that colour” question? It came up in the post about K+ red Ramalinas too. Perceptions vary widely and not everyone has access to the extremely expensive Munsell colour charts. Put “colour chart” into the search on this website and there are a few hits, including one which implies to me that RBG Edinburgh produced a cheapish one for fungal spore prints, but I don’t think it is available any more. Someone suggested trying Dulux paint colour charts as they are widely available, standard and free. Maybe a colour chart distributed at least to BLS members, and maybe including fungus colours could be thought of. And yeah I know they change colour when they are wet, shaded, etc. Nightmare!

Juliet

I am not going to advocate for or against the adoption of a standard colour chart in British lichenology but I have sometimes used the RAL list of colours, readily available online, in some of my discussions and descriptions. Nor am I suggesting that the RAL list would necessarily be the best to use. I am just endorsing the suggestion that the description of colours in lichenology has sometimes seemed inadequate. Take, for example, Protoparmelia oleagina. The LGBI3 description of it is little changed from that given in the 1992 Flora and gives the impression that its thallus is a shade of brown.

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Every specimen I have examined (including herbarium specimens) are, to my perception, a shade of green. The following is from a twitter thread in which I discuss the subtleties of P. oleagina.

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Here is a link to the twitter thread (which includes the ‘K+ oily’ reaction, my own description of the thallus and notes on etymology and ecology of this interesting species).

https://twitter.com/obfuscans3/status/1344427288092438529

Here is a link to the List of RAL colours that I have used.

https://en.wikipedia.org/wiki/List_of_RAL_colours

Mark

I agree, usnic acid colours are a bit difficult to describe in words. Pale grey-green with the merest hint of yellow is resaonable!

Using a colour picker in Photoshop Elements I got a Color Hex of #706b55 for an avaerage section of a Protoparmelia oleagina photograph, for what it is worth

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Neil

Following up further on the K+ brown reaction for fumarprotocetraric acid that Neil mentioned in this thread. In search of a more convincing result, I applied K to another spot on my specimen of Cladonia furcata above. Rewarded with a clear K+ brown reaction, I applied Pd directly nearby. The strong Pd+ red demonstrates the presence of fumarprotocetraric acid, as expected. And the lack of any K/UV+ yellow flurorescence on the K-spot suggests fairly unmistakeably that the K+ brown is due to fumarprotocetraric acid, and not by strange chance to any trace of atranorin, which C. furcata can sometimes contain.

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An interesting note: where Pd overlapped K, the brown reaction became yellow. I wonder what Pd+ yellow compound results from the decomposition of fumarprotocetraric acid in K?

Another interesting note: a Google search on the K+ brown reaction for fumarprotocetraric acid turned up this 1935 article by American lichenologist RH Torrey entitled ‘Paraphenylenediamine: A new colour test for lichens’: https://www.jstor.org/stable/40597010” class=”bbcode_url”>https://www.jstor.org/stable/40597010.

It appears from Torrey’s article that, until Pd came along, some lichenologists relied on the K+ brown reaction for fumarprotocetraric acid to help separate Cladonia species. Neil noted above that the reaction is still mentioned in North American Cladonia literature. And the table of colour reactions in IM Brodo’s 2001 North American flora lists fumarprotocetraric acid as ‘K+ brownish’.

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Torrey suggests that the K+ brown reaction is also detailed in what he calls Annie Lorrain Smith’s ‘Manual of British Lichens’. That’s not a title of Smith’s of which I’m aware. So far as I know, Smith published a field guide entitled A Handbook of the British Lichens (1921), a flora in two volumes entitled A Monograph of the British Lichens (1911 and 1918), and a treatise entitled simply Lichens (1921).

In none of those works by Smith could I find any reference to K+ brown for fumarprotocetraric acid. She mentions only K+ yellow for atranorin in her descriptions of Cladonia species (unless I’m missing something). I also couldn’t find it in the 1913 beginner’s flora by Gustav Lindau that Torrey calls ‘Die Flechten für Anfänger’, though the electronic copy I found online was hard to navigate. (Apparently, the proper title is Kryptogammenflora für Anfänger, Band 3: Die Flechten.)

That isn’t to say the K+ brown reaction isn’t found in any British work: it’s mentioned in in Orange, Smith & James’s 2010 monograph Microchemical Methods (p 12), for example. I also found it mentioned alongside Pd+ red as a diagnostic for Usnea antarctica in this 1964 flora of Antarctic lichens published by the British Antarctic Survey: https://core.ac.uk/download/pdf/33451352.pdf” class=”bbcode_url”>https://core.ac.uk/download/pdf/33451352.pdf. (Incidentially, it’s mentioned as diagnostic for U. antarctica in some online descriptions from Australia and New Zealand that I found in my Google search.)

But anyway: assuming that there isn’t a ‘Manual of British Lichens’ by Annie Lorrain Smith of which I’m unaware, the K+ brown reaction for fumarprotocetraric acid on which Torrey and other (presumably mainly North American) lichenologists relied doesn’t seem to have been much used by British lichenologists before being obviated by the more effective Pd+ red.

Thanks, Alain — that’s an important point. But I think in this particular case we can be fairly confident that the K+ brown reaction that I’ve observed in my C. furcata specimen is due to fumarprotocetraric acid, for the following reasons:

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