Observation 88244: Physcia subtilis Degel.

When: 2011-11-06

Collection location: Riverwalk, Baraboo, Wisconsin, USA [Click for map]

Who: Andrew Khitsun (Andrew)

No specimen available

Proposed Names

29% (1)
Recognized by sight
57% (1)
Eye3 Eyes3
Used references: ID provided by Jason Hollinger

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Eye3 = Observer’s choice
Eyes3 = Current consensus


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I know how that goes!
By: Jason Hollinger (jason)
2015-12-20 23:22:51 CST (-0500)

So frustrating. But you got enough to confirm the id, that’s what matters.

While this specimen intrigued me, and there was plenty of it around,
By: Andrew Khitsun (Andrew)
2015-12-20 23:15:27 CST (-0500)

all were on this indestructible rock (probably quartzite?) and all I could get was very poor material. I apologize…

I’m afraid I didn’t keep this specimen
By: Jason Hollinger (jason)
2015-12-20 23:04:40 CST (-0500)

But my notes claim that the medulla was in fact K- (with no commentary on how difficult it was to come to that conclusion! :). And the lower cortex was prosoplectenchymatous, helping rule out… well, not sure what that helps rule out! Maybe I was just practicing sectioning something that tiny! The handy thing about doing a clean section of the thallus is that you can check for atranorin crystals under polarizing light - a much more controlled and accurate way of determining if there is any atranorin in the medulla. In this case, the cortex was strongly POL+ but the medulla and lower cortex were POL. Clear confirmation of what you initially suspected.

An awful lot of work just to say: “You were right all along, Andrew!” :)

Jason, this is specimen #11172012-4
By: Andrew Khitsun (Andrew)
2015-12-20 22:13:12 CST (-0500)
Maybe this is P. subtilis
By: Jason Hollinger (jason)
2012-11-30 14:58:19 CST (-0500)

I’ve seen more variation in this species than I knew about when I wrote that last comment. The new observations still don’t suggest any other likely options. It is a very difficult species to do the medulla spot test on. I think Brodo even might say that it’s impossible, but I respectfully disagree with whoever wrote that. It is possible, but you really need a better microscope, I think, to have a chance.

I’ve managed to scrape off some of it.
By: Andrew Khitsun (Andrew)
2012-11-29 21:26:22 CST (-0500)

Ended up having almost no lobes in the mix, just pieces thickly covered with either isidia breaking down into soredia, or isidioid soredia. Lower surface pure white, with short stubby rhizines (that’s where the word “hapters” comes to mind, although I think those are even shorter). Dropped K onto the piece, and got darkish stain – I would describe it as very dark yellow to reddish. Pieces are tiny, I haven’t managed to tease out medula yet.

I don’t think so
By: Jason Hollinger (jason)
2012-02-26 14:01:44 CST (-0500)

But I can’t suggest better alternatives. You have a bewildering set of Physcia photos. I would love to go back over them all with a complete key in front of me… and while I’m dreaming, I’d like spot test results and super macro shots, too. :)

Physcia subtilis?
By: Andrew Khitsun (Andrew)
2012-02-25 22:29:28 CST (-0500)

Created: 2012-02-25 22:15:12 CST (-0500)
Last modified: 2015-12-20 22:14:15 CST (-0500)
Viewed: 65 times, last viewed: 2017-06-10 10:40:50 CDT (-0400)
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