|I’d Call It That||3.0||0.00||0|
sum(score * weight) /
(total weight + 1)
|I’d Call It That||3.0||8.56||2||(synan,zaca)|
sum(score * weight) /
(total weight + 1)
I had O. parella mixed up with a different species, apparently. I thought it had much more “showy” apothecia. Excellent apothecial section. You’ve convinced me. Great observation.
[Edit: the Sonoran Flora says this about O. parella: apothecia 0.75-2 mm wide; disc K- C+red KC+red P-; thallus K- C+/-yellow KC+yellow P- UV+/-white; spores 45-65(-88) x 25-40(-50) µm (8 per ascus); on acidic to slightly basic rocks, usually maritime, widespread in temperate northern hemisphere.]
I performed a new preparation to observe under the microscope and this time the result was much better than before. I uploaded photos of the apothecial section and of the asci and spores. The spores are really big, 63.3 × 35 micron in average. I think this lead to the consideration of the genus Ochrolechia and, particularly, to the species O. parella. A very similar specimen can be seen here.
This section might not be quite thin enough to distinguish details in the hymenium (e.g., asci and spores) clearly. You can also try squashing it more. Adding a drop of KOH can be very effective at loosening everything up so that it squashes easily without tearing everything. Note any color changes when you do this.
A very useful technique someone showed me is to place a drop of KOH just beside the coverslip on the left side so that it is touching the coverslip. Then place a piece of tissue paper touching the right edge of the coverslip. You might have to press it down a bit, but it should suck up the water under the slip and draw the KOH through. For transient or weak reactions (like the C+ pink/red due to gyrophoric acid) you want to be watching through the eyepiece the whole time you are doing this, otherwise you’ll likely miss the reaction.
One unusual feature that is very clear in this set of photos is that the margin of the apothecium is curled in and actually overgrowing the hymenium significantly. That might be useful later.
I upload two photographs of an apothecial section of this specimen. How to interpret them?
Here’s a set of images of sections I’ve done. Below is an image of a Caloplaca where the epihymenium and cortex of the margin are reacting K+ red due to anthraquinones. You should have no trouble making similar sections with a suitably sharp razor blade under a dissecting microscope, although it might take a little practice at first.
If you’re just doing a squash preparation, then you’re right, there’s no way to tell what’s what. Then I’d recommend just doing the spot tests under a dissecting scope. Just scrape away the cortex — it usually tears and flakes off fairly easily if you use the corner of a square blade. Scrape away a sufficiently large area so that you can be sure of applying the reagents to the medulla without touching any of the cortex. I used a simple wooden toothpick for a long time with pretty good results. The preferred technique with professionals is a glass capillary tube which has been drawn out under a flame to a very fine point. This lets you pick up tiny quantities of reagent and apply them very precisely.
I would recommend, if you are serious, starting to do sections regularly when studying lichens. It’s both good practice, and you need to do sections to differentiate the anatomy of apothecia. It is important to see color, texture, thickness of hymenium, epihymenium, hypothecium, exciple; to check for oil droplets and crystals; count spores in asci; etc. Spore by themselves only get you so far. Lecanora is a perfect example: they all have the same spores plus or minus, and chemistry only allows you to narrow it down a little: there are still dozens of species that have no reactions and “normal-sized” spores, for example. These are differentiated by, among other things, presence of crystals, size of crystals, thickness and continuity of algal layer, thickness of cortex on top and bottom of margin, etc.
I don’t understand very well the way how to perform the test. In a preparation how do I know what is cortex and what is medula, in order to identify which one reacts with what? Can you give some example of an observation where these tests were made?
You probably have an Ochrolechia then, not _Lecanora. Rule of thumb (according to Brodo in Lichens of North America): spores < 20 µm are Lecanora, spores > 20 µm are Ochrolechia. Both have simple, smooth, colorless, elliptical to globose spores. Usually 8 per ascus, sometimes 4 in Ochrolechia. Lecanora in general is more diverse, so exceptions undoubtedly exist.
Chemistry is very helpful for Ochrolechia. Carefully check K, C and KC (K followed by C) on both cortex and medulla. A particularly good (but painstaking) way to do it is to introduce drop of KOH or bleach at edge of coverslip and draw it through while watching through eyepiece. That way you can tell exactly which tissues contain the reactive substances. Sometimes only the epihymenium, other times just cortex of margin, etc. Also UV is often good since this is a predominantly tropical genus so it often has exotic fluorescing pigments.
I have made a preparation to observe under the microscope, but some thing goes wrong and I’m not sure about the results. The “things” that I was able to identify as spores had the following average measures: 23.5 × 19.65 microns. Is this possible?
In a next opportunity I will try to collect the spores for further analysis under a microscope. In the meantime I’ll try to get some information about the two genera in question.
The apothecia are a bit small, but those super-thick rims are typical of Ochrolechia. Definitely need to dissect and look at spore size, crystals, etc. if it is Lecanora — an extraordinarily large and difficult genus. Ochrolechia would most likely have very large spores; there are far fewer in that genus, although I think the ones on rock haven’t been well studied yet.
Created: 2010-06-25 20:39:27 EDT (-0400)
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