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I had no idea any Punctelia had interesting cortex spot tests! Here I thought they were all the same: cortex K+/- yellow; medulla K-, C and KC+ deep red. I wonder what chemical is giving the C+ yellow reaction in the cortex. I’ll bet those are UV+, as well.
In this observation I made (in situ) only the tests for cortex, not for medulla, and I didn´t bring home a piece of the specimen. So, my sentence " However, the chemical reactions don’t fit any of the species to which my specimen is similar, according to the given reference" referred to chemical reactions for cortex. Now I realize that such sentence was not correct, because, although for the first two species mentioned (P. borreri and P. reddenda) the C-reaction for cortex is said to be C+yellow, for the third one (P. subrudecta) no result in mentioned in the reference (only results for medulla and soredia are given). Therefore, P. subrudecta could be the species for my specimen.
Concerning the way on how to do tests for medulla, thanks to you, with your help in previous MO observations, now I have no problem in performing them.
I think you might be doing the spot tests wrong. Punctelia spp. should have among the ost reliable C+r and KC+r reactions in the lichen “kingdom”. I think it’s just a matter of scraping off a patch of cortex in this case. Here’s a series of photos demonstrating what I call “proper technique” that I just took of a specimen of Punctelia I happen to have on hand.
Hope this helps. Note that lots of other C+ and KC+ reactions are extremely fleeting and essentially impossible to capture in a still-frame (e.g., Tuckermannopsis or Flavoparmelia). However, Punctelia’s reactions are remarkably persistent and strong. So it makes a good test case to make sure you’re doing everything right.
Created: 2010-07-24 13:41:57 PDT (-0700)
Last modified: 2010-08-14 11:38:50 PDT (-0700)
Viewed: 43 times, last viewed: 2017-06-07 19:09:30 PDT (-0700)