Hi all,
I have 2 specimens of what appears to be Physcia dubia. All the the descriptions seen to fit except the P+Y test. All my material comes out P-. Is there another species that fits with the P- result?
The atranorin in the cortex of P. dubia gives a K+ yellow and P+ pale yellow. The latter is usually weak, unless high concentrations of atranorin. So if you get K+Y and P-, no worries, P. dubia could be fine.
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