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First I will look for the material here. If I’ll have any doubt, I’ll let you know. Thanks.
… but that seems a bit overly expensive. Hmmm… Ah, I found my receipt finally. Try http://www.polarization.com (this page in particular). The problem I ran into was that 99% of the polarizing filters sold on-line are for cameras: I just wanted a sheet of the stuff.
Here’s what I did, for whatever it’s worth: I got a cheap heavy-duty sheet which I cut into 10 × 10 cm squares; this I hold between the microscope light source and the stage. Then I got a small piece of thin, high-quality, high-transmission film; from this I cut a tiny circle which I placed permanently inside the eyepiece of the microscope. (This required a bit of patience and skill in order to avoid introducing dust, and to make sure it was perfectly flat and uniform and covered the entire area. But once done, it lasts forever.) I just keep the square filter close to the microscope, and hold it by hand whenever I want to check for crystals. Very easy and handy.
Are available on-line. If that’s too expensive, I can send you a piece of the sheet I bought. I find it an extremely useful tool, so I’m happy to help you acquire it. (Sorry, I can’t find the address of the place I bought mine.)
In particular, the warning about the esistence of falsely-septate spores makes all sense for people like me, whose equipment is bad. I don’t that was the case, but …
Unfortunately, I don’t have polarizing filters to make the analysis of cristals.
I started to try to follow a key, but with no sucess. L. subfusca group seems a reasonable choice, but there are too many species in this group.
This looks like one of the L. subfusca group based on the pale gray lumpy K+y thallus and well-developed rims and reddish-brownish disks.
Be careful of falsely-septate spores among Lecanora and Lecania and kin. Spores can often have bubble or oil-drops in them which will make them appear to be multicellular even when they really aren’t. Mounting the section in KOH (or better yet, drawing KOH under the coverslip after observing in water) will often help clear this. Even so it can be easy to get it wrong in either direction, resulting in the wrong genus: a very frustrating experience!
A very useful diagnostic character in Lecanora is the presence of crystals, both submicron granules impossible to see and larger blocky things up to dozens of microns wide which are easy to see in a simple water mount. If you have access to polarizing filters, it will really help: place one filter below the stage, then the other on top of the eye piece. Rotate one of them until they are at 90° from each other. When oriented like this, all light is blocked except where it passes through something crystalline (which causes the polarization of the light to rotate) making the crystals show up bright white against a blue-black background — even when too small to see. Furthermore, observing whether these crystals persist or dissolve in K is also helpful. In descriptions on CNALH you will see things like “minute crystals in epihymenium clearing in K” — this is what that refers to.
In particular, if you are seeing a K+y reaction (possibly from atranorin in the cortex), there is good reason to suspect minute crystals in the epihymenium which clear in K. In addition to that, the L. subfusca group should also have large crystals in the rim of the apothecia which are insoluble in K. Spore size and thickness of the apothecial cortex can then help distinguish the individual species within this group.
Created: 2011-09-14 08:21:40 NZST (+1200)
Last modified: 2011-09-14 08:21:43 NZST (+1200)
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