Observation 203390: Physcia (Schreb.) Michaux

When: 2015-04-24

Collection location: Sintra, Portugal [Click for map]

Who: zaca

No specimen available

Growing on bark.
Underside brown, whitish at the margin of lobes. Rhizines short and indistinct.
All chemical reactions negative on thallus and medulla.
The first three specimens were found at a shaded place while the last one in a more sunny habitat. I believe they are all of the same species.

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Yeah, the description …
By: zaca
2015-04-26 13:13:49 PDT (-0700)

of Physcia sorediosa fits quite well, apart from being non-fertile specimens. So, I repeated the K test on medulla at four distinct points. The result remains the same and, maybe, at one I could read it as K+ very pale yellow. Taking into account your comments about Parmeliopsis, that I never saw, perhaps it is better to leave this as Physcia.

Oh, sorry, I keep forgetting to re-read the notes!
By: Jason Hollinger (jason)
2015-04-26 12:12:27 PDT (-0700)

You’d already answered myquestions. Here’s a description of Physcia sorediosa:

Underside black or dark brown (paler towards tips); rhizines black, moderately abundant. Soralia marginal (according to Moberg; mostly laminal according to Hale), small and delimited, round, often pustular, often best developed in lobe angles, occasionally becoming capitate; soredia coarse. Lower cortex paraplectenchymatous. Zeorin present. Upper surface whitish gray to gray, shining or rarely pruinose, usually ±distinctly white maculate (but rarely so in N. American material). Thallus closely adnate, 2-4(-5) cm broad; lobes crowded, usually imbricate, ca. 1(-2) mm wide, usually widest near the tips. Apothecia rare, to 2 mm diam; margins crenulate or sometimes sorediate; disc black, with or without pruina; spores Pachysporaria-type, (17-)20-26(-28) x 9-11(-12) µm. Pycnidia rare. Medulla K+ yellow. On bark (oak and other hardwoods) in open areas, and occasional on rocks, southeast coastal plain (N. American range).

These photos look like typical material.

I uploaded a photo of the underside.
By: zaca
2015-04-26 09:45:31 PDT (-0700)

As said in the notes the first three specimens lived in a shaded place.
Dirinaria I don’t think it exist here and I never saw references to it;
The rhizines are short and black as one can notice near the margin of lobes.
Physcia sorediosa is not mentioned in the British Flora and doesn’t appear in the checlist for the Iberian Peninsula, but it exists in the archipelago of Azores.

Haha! Okay, forget Pyxine… but I still don’t think this can be Parmeliopsis
By: Jason Hollinger (jason)
2015-04-26 09:02:02 PDT (-0700)

Parmeliopsis is shiny, never pruinose, lobes are flat not convex, and the soralia start out at least very briefly as warts and I don’t see any sign of warts preceding the development of the soralia on yours anywhere in any of your excellent photos.

Are these black below? Rhizines?

I see some Normandina pulchella in one photo, so I infer that this is a particularly shaded location. Maybe the concentration of atranorin (a sunscreen) is just really low, accounting for the weak K reaction on the cortex.

If we are admitting the possibility of K+y cortex, then we’re obliged to consider Physcia and Dirinaria (rhizines?), too. If black below, then what about Physcia sorediosa?

Interesting puzzle!

Don’t talk me about Pyxine
By: zaca
2015-04-26 04:22:15 PDT (-0700)

Because it seems to be a genus ignored to exist here and, looking to my observations, it can have various representatives species; Precisely the day after this observation (25-04), I found another one that I’ll post soon. However, in this case I don’t think this is Pyxine, because the medulla is white and the Pyxine with this feature that could exist here is only restricted to P. cocoes, which is different from this and I conclude to be the case of the one I’ll post.
Now about the chemical reaction. The British Flora considers two species of Parmeliopsis both with medulla C-, K-, KC-, P. ambigua and P. hyperopta and describes the reaction on thallus as K+ faintly yellow and K+ pale yellow, respectively. Maybe, there is a BIG difference between the two and how it compares with K- (observed at night with artificial light, as was my case). I just repeat the test with daylight and accept any of the three (K+ faintly yellow, K+ pale yellow or K-) for this specimen and, perhaps, now I’ll describe it as K+ yellowish (another vague term!).
Thanks, Jason, for your comment and opinion.

Could this be one of the Pyxine with lichexanthone instead of atranorin?
By: Jason Hollinger (jason)
2015-04-25 19:15:34 PDT (-0700)

Those could be completely negative (except UV+ bright yellow)…

Parmeliopsis spp. should be either K+y or KC+y on top.

Created: 2015-04-25 17:10:51 PDT (-0700)
Last modified: 2015-04-27 15:40:02 PDT (-0700)
Viewed: 67 times, last viewed: 2017-06-19 23:59:24 PDT (-0700)
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