Observation 159553: Parmotrema A. Massal.
When: 2013-12-12
No herbarium specimen

Notes: Found in a low lying forest of Loblolly Pine, American Hornbeam, Overcup Oak, Swamp Chestnut Oak, and Water Tupelo.

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By: Tim Martin (T Martin2010)
2014-02-18 17:45:21 PST (-0800)

Thanks Jason for the chemistry tips! I meant to thank you earlier for such a thorough primer.

Just a few tips first…
By: Jason Hollinger (jason)
2014-02-11 17:40:58 PST (-0800)

If you can find NaOH, then try to dissolve as much as possible in a few cc of water. Stronger is better. (But watch out, it’s an exothermic reaction! :) That will last for months maybe even years if stored in cool quiet dark place. Once mixed up, no need to ever shake it or stir it up again, that will just cause the stopper to dissolve and corrupt the solution quicker!

Okay, so you want to test the medulla. This is critical! (This is where the dissecting scope comes in handy. :) Scratch off the grey cortex with the corner of a razor blade or the tip of a sharp knife or something, exposing the fluffy white medulla. This is, naturally!, extremely hydrophobic, so it’s not always easy to apply the reagent (K = KOH/NaOH, C = bleach, KC = KOH then bleach, separately, but in sequence on the same spot). Toothpick, needle, paint brush, capillary tubes, whatever works.

I like to impress on people the importance of applying small controlled amounts. KOH will dissolve everything, so if you apply too much to a small structure it’ll just turn it transparent and end up looking brownish or greenish or some other inconclusive color. And apply enough bleach and everything will turn colorless eventually! You want to check what the color is immediately after you brush just a tiny bit on, then watch how it changes. This is more important when testing the cortex (especially if the cortex is thin). The K+y of the cortex (all of these Parmotrema should have K+y cortex) is kind of faint, and it is quickly muddied up when the cortex turns transparent and lets the green from the algae through. The medulla is easier, fortunately, especially when it’s nice and thick and fluffy like with these Parmotrema.

The K+y should be strong (stictic acid?). And the C+/KC+r should also be very strong (lecanoric acid?). The other (protocetraric acid) is ambiguous. It will often be faintly K+ yellowish, sometimes noticeably so; it will be completely C-; and the KC+ pinkish is very subtle, hard to describe and variable. It can be just a brief flush of pink immediately fading to nothing or faintly yellowish. Or it can be a relatively strong rose/orange/pink that slowly fades or changes color, typically toward the yellowish/orangish end. It all depends on the concentration of the substance and the reagents applied to it. And maybe the phase of the moon.

By: Tim Martin (T Martin2010)
2014-02-11 16:47:51 PST (-0800)

I have the specimen. So this is where i would use Red Devil Drano? It is going to be red, pink, or yellow?

Okay you win, chemistry important here
By: Jason Hollinger (jason)
2014-02-11 16:23:15 PST (-0800)

This is probably P. austrosinense or P. gardneri, but need chemistry to tell which:

P. austrosinense – K- C+r KC+r
P. gardneri – K- C- KC+ pinkish
P. perlatum – K+y C- KC-

All other sorediate species expected there should have conspicuous cilia.

Created: 2014-02-11 15:40:22 PST (-0800)
Last modified: 2014-02-11 15:40:30 PST (-0800)
Viewed: 26 times, last viewed: 2016-10-22 09:18:37 PDT (-0700)
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