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advice / recommendations / ways of reading the chemical reactions in lichens, which serves as a guide to procedures and techniques to take into account. I’ll try to get in future observations the results of the medulla tests, since these are more informative and reliable than the tests in the thallus, although these are easier to do.
Regarding this observation, it seems to me that, based on your interpretation about what black dots are, the species should be Parmelina quercina or one of its variants, that the article mentioned by Chris in his last post shows us (by reading the abstract, since they do not have the article). I take this opportunity to thank Chris for this reference.
If possible, I would like to have your comment about the observation MO65581, I just created, where it seems there is also a species of Parmelina or of some very close genus.
First, I would personally suspect that black dots, especially if appearing flush or bulging slightly from the surface, are pycnidia, not budding isidia. Isidiate species (and sorediate species) almost invariably produce isidia (and soredia) from a very early stage, much earlier than a fertile species would begin to produce apothecia (which apparently require a much greater investment). Fertile species, for whatever reason, frequently also have pycnidia. Sometimes sterile species do, but it’s a useful correlation: abundant pycnidia on a thallus with no soredia, isidia, or apothecia generally indicates an immature fertile species. (I’ve heard suggested that the conidia produced by pycnidia can actually function as “sperm” or “pollen”, a very inrtriguing possibility.)
The other, and more important point, is the importance of distinguishing chemical spot tests done on the cortex versus on the medulla. I, too, am convinced that this specimen is Parmelina, which as you point out should have lecanoric acid in the medulla, and atranorin in the cortex. Lecanoric acid is a particularly satisfying substance because it produces gorgeous, immediate, lasting, vivid, dark red with both plain C and with K followed by C. Nothing subtle about it. However, the cortex will block the C from reaching the medulla, but while lecanoric will be entirely K-, atranorin in the cortex will cause the standard ~slow (takes a fraction of a second, but not immediate) soft yellow reaction. K can cause the cortex to “liquefy” over time, so subsequent application of C can actually penetrate somewhat to the medulla, and since the C+r reaction is so strong, you’ll see it through the K+y.
Sorry to belabor the point. This is all just to illustrate how tricky even “obvious” reactions can be to interpret. In an ideal world, you’d put a fragment of the lichen under a dissecting scope, scratch/slice a patch of the cortex off with a razor blade, then apply a very small fraction of a drop of K to both cortex and exposed medulla, then C, then add more C on top of the K. (Common applicators include: toothpicks, needles, capillary tubes with drawn tips, even tweezers will work in a pinch… I’m so sorry, I had no intention of making such a bad pun…) With C in particular, you will get more satisfactory results if you use the minimum amount possible, somewhat counter-intuitively. It’s as if C will “bleach” out the very reaction that it causes, thus over-application will make the fleeting C+ pink reaction of gyrophoric nearly impossible to detect, while just brushing it lightly will leave a bright pink-red streak that may last for seconds. And in any case, applying small amounts guarantees that the reaction only involves the particular part of the anatomy you are interested in: the surface of the cortex and the interior of the medulla in this case. (Other times you will want to test only the soralia, or the upper part or lower part of the medulla, or — the trickiest by far — the inner and outer parts of apothecia of Ochrolechia and Pertusaria.)
Failing such controlled conditions, I’m sure you can work something out in the field where you scratch the surface off with the tip of a pocket knife, say, and use some sort toothpick or other object to apply the reagents (instead of an eye-dropper, for example!)
Argüello, A., R. del Prado, P. Cubas and A. Crespo, 2007, Parmelina quercina (Parmeliaceae, Lecanorales) includes four phylogenetically supported morphospecies, Biological Journal of the Linnean Society 91: 455-467. (This link is to the first page of the paper only.)
… I was undecided between the two species P. pastellifera and P. tiliacea. With her comment a new hypothesis appeared: P. quercina. All these species appear in the Checklist of lichens and lichenicolous fungi of Portugal (where Parmelia quercina is referred instead of Parmelina quercina, but these are synonymous).
In the meantime, I had acess to the work of Hale A Monograph of the Lichen Genus
Parmelina. Reading it, I learned that these three species form a consistent group within the genus Parmelina, characterized by the presence of lecanoric acid, which produces chemical reactions KC+red in medulla. In this work the species P. pastillifera is singled out by a very special form of isidia, “peltate isidia”, which is described and pictured in detail and for which, I think that, observation MO52255 constitutes a good example. So, we are left with the two other species, and the main question concerning the identification is to know if the black dots that appear in some of the lobes in the thallus are isidia, in which case the specimen should be P. tiliacea, or are of different nature, e.g. pycnidia, and in this case the classification would be P. quercina. I am not able to decide, but maybe someone can.
As a curiosity, in the above mentioned work o Hale, the photograph that illustrates the species P. tiliacea was taken from the work of the Portuguese lichenologist Sampaio.
Evenly colored, gray, black below, no cilia… There are only a few parmelioid genera that are like that. Myelochroa, Parmelinopsis, Bulbothrix all have minute cilia, and might not occur in Portugal (they’re eastern species in N Amer, your genera are all same as our western genera). Canoparmelia has mottling and/or cracking, as does Parmelia. I don’t think there’s anything left but Parmelina? We have a non-isidiate species in California, P. quercina. Wonder if you have it, too? Medulla is K-, C+r, KC+r (lecanoric acid). There are ~10 species in the world, and all will be K-, C+/- pink or red, and KC+/- pink or red.
Created: 2011-04-13 18:16:38 EDT (-0400)
Last modified: 2011-04-13 18:17:20 EDT (-0400)
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