Observation 165548: Physcia tribacioides Nyl.
When: 2014-05-17
Who: zaca
No herbarium specimen

Proposed Names

29% (1)
Recognized by sight: Wonder if this is a Portuguese Physcia sp.. What are the candidates? P. dubia, P. tribacioides, and … what else?
58% (1)
Eye3 Eyes3
Recognized by sight

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Eye3 = Observer’s choice
Eyes3 = Current consensus

Comments

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Oh, stupid me…
By: Jason Hollinger (jason)
2014-05-19 14:38:05 PDT (-0700)

I mistook P. tribacioides for P. tribacia! Yes, of course, this looks just like your other P. tribacioides, and matches the description in British Flora nicely. Definitely should keep my nose out of other continents!

Jason, do you still
By: zaca
2014-05-19 14:29:58 PDT (-0700)

rule out P. tribacioides based on the result of the K test on medulla?
The other species are unknown to me. The other tests I will do when I’ll have oportunity.
Thanks for the suggestions.

I would rule out P. dubia and P. tribacioides
By: Jason Hollinger (jason)
2014-05-19 13:31:06 PDT (-0700)

based on the position of the soredia (those have coarse soredia at or just under the tips). How do you interpret it? I see fairly irregular laminal soralia with rather fine soredia. P. americana also has laminal soralia, but I’m used to the soralia being more regularly round and raised, almost hemispherical to capitate. Looking through Sonoran Flora… What about P. poncinsii? I have ided a few specimens as this, but without much confidence.

Have you done a K test on the medulla? The other thing that can help is doing a section of the thallus to see if the upper and lower cortex are made up of obviously round or blocky cells (paraplectenchymatous). You can try to shave a very thin sheet off the top and bottom cortex, but I find that extremely difficult to execute (although, when accomplished, it makes reading the cellular structure very unambiguous). Instead, I think you can get away with a vertical section across the lobes or lengthwise (I’m not sure if it makes a difference). If it’s paraplect. then it will have obvious round / angular-blocky cells in a line; if it’s not (i.e., if it’s prosoplectenchymatous), then the cellular structure just tends to be obscure. Kind of unsatisfying, but each time I see a true paraplect. cortex with this method, I become more and more confident of diagnosing the prosoplect. cortex, too.

Created: 2014-05-19 11:40:37 PDT (-0700)
Last modified: 2014-05-19 15:32:59 PDT (-0700)
Viewed: 25 times, last viewed: 2014-05-20 03:55:35 PDT (-0700)
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