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It feels like this should be an “easy” genus, but even with access to microscope and chemistry, I rarely get a confident ID. There are undoubtedly possibilities other than C. atroflava. But keep in mind variability; I’d say it is still plausible.
The specimen lives on a basaltic rock. Relatively to Caloplaca atroflava, I did not find much about it: I was able to see only two photos of this species (not very much similar to my specimen) and the following description taken from here:
“This species has a thin crustose thallus, dark-grey in colur and cracked-areolate (like crazy-paving) when well-developed. Apothecia are 0.5mm diam. scattered to crowded, with brown-orange discs and bright orange margins. The wide ascospores with a broad septum are diagnostic.
Chemical Tests: Apothecia are K+ purple, whilst the thallus is faintly K+ purple in places.”
It seems that is an uncommon species. For a positive identification maybe the size and the septation of the spores will help. For now this is out of my possibilities.
Sure enough, though, I see there are a few species with C+ red apothecia. Caloplaca atroflava is dark gray thallus, dark red-orange disk, variable margin, epihymenium K+ red and C+/- red, growing on non-calcareous rocks. It is known from Europe. The substance responsible for the C+ red reaction is apparently unknown in this case. [source: Lichen Flora of the Greater Sonoran Desert Region, Vol. III. 2007. Treatment by Cliff Wetmore.]
Some purplish appeared both with K, C and KC, visible mainly at the periphery of the drops. With C the inner part of the discs reacted red.
Sorry, about the colors of the photos. Somehow the camera was regulated for artificial light and not for the day light.
Yes, it is on rock. The color is indeed bright orange. According to the sites I saw my impression is that it could be C. crenularia (see here), that usually lives on rocks. You can see more photos of some apothecia in observation MO49423 (all pictures there except the first one). I know where it lives and tomorrow I will make the spot tests.
Is that on rock? Looks like it has a gray thallus and maybe even gray outer margin on the apothecia. A bit like C. cerina but on rock. I wonder if that’s unusual. The color looks a bit off in the photo: is it clearly bright orange in person? If you happened to have it, the K test will easily remove all doubt.
Created: 2010-07-31 16:52:05 CDT (-0400)
Last modified: 2010-08-14 14:38:53 CDT (-0400)
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