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They’re just making it too easy now. You do know whether your specimens are “rough” or “smooth”, right? You might need tweazers to count the spores, too… :)
Brodo in Lichens of North America claims the P. plittiana only has norstictic acid in the medulla, however I have notes of specimens (maybe a different species?) in which both cortex and medulla has it. In all my cases, the test was very clear; I invariably called it “bright red”.
I wonder, though. Maybe you just have a population with very low concentration? I’ve seen other species (e.g., a graphoid thing in Florida) which were just K+y without any hint of red, not even any crystals under the compound microscope, but which nevertheless were determined by professionals to be species which contain norstictic acid. I get the idea that the various xxx-stictic acids are all very similar, and always co-occur, and that it’s just the relative quantity that’s “fixed”. That is, some species mostly produce norstictic, others mostly stictic, yet others constictic, etc. It therefore wouldn’t take much of a mutation to switch it to produce more stictic than norstictic. Just a thought…
Here’s another thought. There’s a key to all species of Pertusaria in the world on-line. (Zaca has mentioned it a number of times in his observations, shouldn’t be hard to find with a google search.) … Sorry, I’m having trouble writing this with a straight face … Clearly that is the answer to your problems.
Need any more “help”?
K test didn’t check out for the species mentioned – medula turned light yellowish, but upper cortex (both on top and at the site of cut) turned darker orangish. Also, there might be several species here, since all kinds of specimen were present – warty and the ones that are just areolate but almost flat. All of them incorporated grains of sand into their thallus to some degree – with flatter bodies having more grains in them. Go figure…
Created: 2012-07-17 18:17:52 PDT (-0700)
Last modified: 2012-07-17 18:21:10 PDT (-0700)
Viewed: 37 times, last viewed: 2016-02-10 12:55:16 PST (-0800)