Notes: The specimens considered in this observation grew on the trunks of very old and well developed shrubs that make the interface between the cliff over the sea and the mainland. During many time got no idea of what these could be, but I saw that, though many of the apothecia are lecanorin type, some appeared as lirellate. This was the first step that lead me first to the genus Enterographa , of which I had never observed a specimen, and after to the closer genus Schismatomma, which differs from the former by the existence of a thalline exciple in apothecia (Ref. 1).
Here are some of its main features:
- Thallus grey-lilac-orangish (maybe due to the Trentepohlia photobiont) pruinose or covered with thin soredia;
- Apothecia mostly rounded but some elongate, disc dark-brown surrounded by raised whitish thalline rim very pruinose;
- Asci with 8 spores spiralled arranged,
- Spores slightly curved, +/- narrow-acicular, ends narrowed, 3-septate, with the following dimensions corresponding to two measurements in two different specimens:
1) Average: Me = 34.1 × 4.7 µm ; Qe = 7.3 (N=24); Ranges: 30.7-37.2 × 3.7-5.5 µm;
2) Average: Me = 30.7 × 4.9 µm ; Qe = 6.3 (N=22); Ranges: 24.9-34.5 × 4.2-5.7 µm.
I think that all the above mentioned characteristics are well documented in the photos attached.
The next problem was to find a name for it and in my opinion that is not yet satisfactorily accomplished. First of all there is a species – S. graphidioides – with (almost) all the above features, including the dimensions of the spores; However, according to Ref. 1, such species lacks soredia and has all chemical reactions negative, while my specimens are either pruinose or sorediate and I will not describe the chemical reactions all as negative (see the corresponding photo attached). While the first question can be related with a distinct habitat from the British Islands the second is more difficult to justify. Trying to find a solution for this problem I search in the web for more information. I saw in Ref. 2 (Stridvall, of course) photographs of a sorediate species – S. pericleum – very similar to my specimens. Unfortunately, I was not able to see a description of this species.
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(norstictic acid, etc.) apparently don’t degrade, even after dozens of years in the herbarium. I got reliable spot tests off of specimens collected in eastern Washington back in the 1960’s and 1970’s.
I have to confess that I can never read the spot tests in your photos. I had no idea that was K+ yellow! I don’t know why, but I have to see the immediate transient results under a dissecting scope in order to interpret spot tests. Maybe I invested so much effort trying to come up with a methodology that I could trust (using dissecting scope, etc.), that I now rely on it completely. Probably a bad thing, but there it is. :(
that lead to another question: I long after collect a specimen are the tests reliable?
The fact is that I collected last week the sample I mentioned. Is it not to late for essaying a P reaction?
Moreover, in that case the question is not the K-reaction, which was clearly yellow, but the KC-reaction, which was immediately red.
You can test for norstictic acid easily enough by looking for needle-shaped crystals when mounted in K under the microscope. Norstictic also bleeds conspicuously yellow when you pass K under the cover slip under a microscope. I think stictic and salazinic bleed yellow, too.
Oh, right, and PPD usually works even on thin thalli – it doesn’t dissolve the hyphae, so if it’s P- it leaves even the thinnest thallus completely unchanged. And most things that are K+ are also P+ (atranorin is only very weakly and slowly P+ yellow, perhaps the one exception). Come to think of it, the keys James Lendemer is creating for eastern North America almost always rely on P for groups like Graphidaceae instead of K. I’d always wondered why. Maybe this is the reason?
Otherwise, if I get K+ red (no matter how seemingly obvious) but can’t see anything under the microscope, I’m forced to conclude it’s probably really K-. (But mostly, I just try to work without chemistry in such cases, at least as much as possible.)
Your re-warning seems entirely plausible, since these specimens grew on old shrubs whose bark is naturally cracked.
I´m also facing this problem in other genera and substrata. Quite recently, I got a specimen (of Buellia, maybe) for which have strange chemical reactions (for the genus); such species has a very thin thallus and the bark of the tree where it lives is also very thin (birch). What to do in such case? To scratch the thallus a bit is out of question, which could be maybe done for the specimen in this observation when collected (due to the scurfy consistence of the thallus) and to observe under the microscope has a similar problem, since it is virtually impossible to obtain pieces of the thallus without the bark of the host.
Reading spot tests is not always easy. There is surprisingly a lot of room for interpretation. Case in point are these specimens with very thin whitish thallus. K will dissolve the thallus readily and expose the substrate, and I frequently get false K+ reddish-brown reactions just like this. Despite that reaction, this specimen could well still lack all secondary substances.
There are various tricks you could try in order to improve confidence: Apply K under the coverslip of a microscope and watch for color changes or bleeding or crystals. Or you could try scraping off just the very top-most layers (avoiding getting any of the substrate) onto a slide or tissue paper, then applying K there. I wish these were unambiguous. But sometimes the only way to be sure is TLC.
Anyway, just a caution to keep an open mind about whether this really is K+ or not…
(Now soredia are a different matter, I have no comment on that!)
Created: 2014-05-20 22:34:41 BST (+0100)
Last modified: 2014-05-20 22:35:00 BST (+0100)
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