Observation 93436: Arthonia Ach.

on driftwood – really thought it was A. radiata, but now have misgivings, e.g. Smith et.al has it as 3-septate and Brodo’s key has it as “spores with 4 equal-sized cells” (they don’t mention variation while these are uniformly 4-septate)

COMPARE with http://www.sharnoffphotos.com/...

need to work on this, but any suggestions would be appreciated

Species Lists



Proposed Names

83% (1)
Used references: Smith, C.W., Aptroot, A., Coppins, B.J., Fletcher, A., Gilbert, O.L., James, P.W. and Wolseley, P.A. (2009) The Lichens of Great Britain and Ireland; Brodo, Irwin M., Sharnoff, Sylvia Duran and Sharnoff, Stephen (2001) Lichens of North America
Based on microscopic features: see micro-photos, spores average (little variation) 16×6u 4-septate

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= Observer’s choice
= Current consensus


Add Comment
on bleach
By: Richard Droker (wanderflechten)
2012-05-09 22:17:49 CDT (-0400)

Thanks Jason. I had some old pleated plastic bottles for darkroom chemicals, and will use them for bleach if I can find them.

By: Jason Hollinger (jason)
2012-04-30 13:52:34 CDT (-0400)

For whatever it’s worth, my recommendations concerning C reagent:

First, do not dilute it! Stronger is always better for K, C and P, but especially C. I’ve never had a false reaction from an overly strong reagent.

Second, the reason C goes bad so quickly is that bleach out-gases chlorine. I find that it helps immensely to keep your reagent bottle full to the top, and replace the cap immediately. I can now keep C for months without changing it. Granted, it lasts longer the less you use it — i.e., the less often you open and close the bottle.

much thanks to Curtis…
By: Richard Droker (wanderflechten)
2012-04-30 13:43:45 CDT (-0400)

I really appreciate expert assistance! Didn’t get a reaction with C, however my C reagent now only gives a mild red with Parmotrema tinctorum. Guess I’ll get another gallon of bleach, do the test again and report back.

Don’t know why my C goes bad so soon. I’ve tried different brands, keep it in the dark etc. I use about 1cc per gallon.

By: Jason Hollinger (jason)
2012-04-28 14:54:15 CDT (-0400)

Curtis writes:

Looks like the Arthonia pruinata group. It should be C+ jaw-dropping red. There’s interesting variation in A. pruinata and relatives that suggests either additional taxa, or just, well, variation. There might be two distinct chemotypes around Deception Pass (I studied this at Redondo Beach nearby), and these may have different spore sizes. The degree of pruinosity seems to vary among thalli that are otherwise identical, or even among apothecia on the same thallus.

It is indeed beautiful! I wasn’t happy with my own photos of this species, but shows a more heavily pruinose form.

Beautiful set of Arthonia
By: Jason Hollinger (jason)
2012-04-28 04:10:17 CDT (-0400)

Thanks, Richard! Curtis loves this benighted genus, maybe he’d be willing to look at this and make some comments…