Notes: Growing on siliceous substrata.
Some features of this specimen:
Thallus: white, chalky and more or less cracked (similar to what I have found before in Diplotomma spp. in calcareous habitats), no prothallus;
Apothecia: black with a white rim around, convex, semi-immersed in the thallus, less than 1 mm in diameter;
Chemical reactions on thallus: C-, K-, KC-;
Hymenium: hyaline, ~ 65 µm tall;
Asci: elongate-clavate, Lecidea-type; 8-spored;
Spores: Only three observed, hyaline, simple, ellipsoid, with a big central circular oil drop, average dimensions: Me = 15.7 × 7.4 µm; Qe = 2.1
The key in the Bristish Flora (Ref.1) for the genus Lecidea gave no answer. I saw in Ref.2 a species with similar macro features, Lecidea umbonata, that has smaller spores (10-13 × 5-7 µm) and prefers calcareous substrata. I was not able to find any other similar.
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Maybe I just wanted to prove that I really do still have something to offer, ha! But this is certainly not the first specimen you’ve posted where we are having trouble even guessing the genus. Eventually — and probably soon, judging by the rapid progress you are making! — this is going to be a common problem. I’m just recommending that you start trying to do ascus stains. Especially on genera that you’re sure of (unlike this!). Good way to learn.
As for this specimen, the field of options is very broad. Hardly know where to start. :(
The read of the asci stains is a long way to walk and this particular specimen is not a good one to start with, since it has only a few asci with spores inside, maybe due to youth.
Thanks, Jason, for the instructions that certainly will be useful in the future.
These black lecideine crusts are hard to make progress on without staining the ascus, unfortunately. For example, if this had a porpidia-type ascus (blue tube structure down center of the ascus tip but otherwise hyaline), it would really help narrow down the genera it could be. Are you ruling out Lecanora based on the red-brown hypothecium? (Superficially it could maybe be Lecanora oreinoides, e.g.)
You’re getting really good with your microscope. If you haven’t already, I’d recommend starting to work on learning to read ascus stains. It’s a long hard road, but you will get there, and it’s so totally worth it. It’s a bit involved, unfortunately: mount section in water, draw KOH across the coverslip, draw water across coverslip next, then finally draw Lugol’s solution across. If the section is thin, once the Lugol’s finally reaches the section (this is why rinsing with water is so important after pretreating with KOH!), you can usually squash the section again with a pencil eraser or something, then wipe the coverslip clean of marks to get good resolution. This should (hopefully!) separate out the stained asci and make it as good and clear as you’re ever going to get. If the asci are still all bound up in paraphyses, it’s hopeless. :( Porpidia and Lecanora are good ones to start with. Lecanora-type (and lecidella-type) asci have a very subtle lighter “axial canal” through the otherwise solid blue tip. Lecidea-type asci are really hard (for me). They’re supposed to have just a dark cap over an otherwise hyaline tip. It just comes out as ambiguous to me. :( It’s all about practice, practice, practice. It’s like learning to read x-rays! You know how a doctor can see the faintest crack in an x-ray and it will seem obvious to them? Same thing with ascus stains. At first they’re so unbelievably subtle I couldn’t believe anyone could read them. Now after a few years of trying and failing, they’re starting to almost seem obvious… at least in some cases! :)
Created: 2015-03-23 18:36:08 CDT (-0400)
Last modified: 2015-03-23 18:37:57 CDT (-0400)
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