Observation 87760: Physcia aipolia (Ehrh. ex Humb.) Fürnr.

When: 2012-02-13

Collection location: White Lake, Oakland Co., Michigan, USA [Click for map]

Who: Insomnia

Specimen available

Amyloid reaction induced by Iodine staining of Apothecium.

8 Septate Ascospores per Asci.

Thallus ranging from pinkish when dehydrated, to grey and greyish-blue when hydrated.


Narrow Lobes.

In progress. Will finish and organize in a couple hours.



Proposed Names

6% (2)
Recognized by sight
Based on microscopic features

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Eye3 = Observer’s choice
Eyes3 = Current consensus


Add Comment
Sure thing
By: Jason Hollinger (jason)
2012-02-15 10:18:28 PST (-0800)

This is a tricky (but important) test with Physcia because (nearly?) all species of Physcia have atranorin in the cortex. So you have to be careful not to get a false positive from applying too much KOH and getting bleed-in from the cortex. Easiest technique is to scratch the upper surface using a pocket knife or razor blade to expose the white medulla (preferably under a dissecting microscope if you happen to have one!), then apply KOH with the tip of a needle or toothpick or capillary tube. (Many lichenologists like to draw out the end of a capillary tube over a flame to get a super-fine point. This is very effective for applying tiny amounts of reagent to very specific spots on the thallus. But admittedly not always available at the corner pharmacy!) If you apply KOH to just the medulla, you will see the K+y reaction immediately if it’s there. It’s totally unambiguous. Just be careful not to get bleed-in from the cortex. You can do all of this using a hand lens or magnifying glass, too, but it’s just more annoying because you kinda need three hands.

Most literature on Physcia, incidentally, talks about K+y medulla being associated with zeorin never mentioning atranorin in the medulla. This is emphatically wrong. Zeorin doesn’t show up on any standard spot tests; it is K-. It just so happens that most (BUT NOT ALL) species with zeorin also have atranorin in the medulla. This was a point of considerable confusion for me for years!

(NaOH or the kind of drano that comes as crystals, like Red Devil brand, also works, if you don’t have access to KOH. Just dissolve as much as you can in a small amount of hot water. Stronger the better. It’s caustic stuff, so you should nominally be careful of spilling it on yourself(!), but I haven’t killed myself. Yet. :)

I was hoping you would stop by Jason, could you please specify?
By: Insomnia
2012-02-15 01:27:00 PST (-0800)

Not exactly sure how to preform that reaction. Could you possibly explain more?

Spores not so helpful for this group
By: Jason Hollinger (jason)
2012-02-14 11:20:44 PST (-0800)

P. aipolia and P. stellaris have overlapping range of spore size. Presence of atranorin (K+y) in the medulla is the most reliable distinction. P. aipolia tends to be more white-mottled, but I’ve seen some strongly-spotted stellaris.

Created: 2012-02-14 01:39:15 PST (-0800)
Last modified: 2012-02-14 11:17:41 PST (-0800)
Viewed: 69 times, last viewed: 2018-01-04 21:28:27 PST (-0800)
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