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Caloplaca discolor (Willey) Fink
Family: Teloschistaceae
Caloplaca discolor image
Stephen Sharnoff  
Thompson, J., 1997. American Arctic Lichens: The Microlichens.
Thallus whitish to yellowish white, with round to irregular soralia scattered to grouped on the upper surface, containing yellow to orange-yellow soredia, thin; the sections with a necrotic upper layer over a cortex which is irregularly K+ purple but which may not show the K+ reaction on gross thallus application, the soredia K+ deep purple, other color reactions negative. Apothecia very uncommon, 0.6-1 mm broad; margin pale orange; exciple hyaline and partly radiate and covered by a thalloid margin, which is more or less paraplectenchymatous, and with the algae more or less glomerulate and mainly below the apothecium, so that the margin may appear biatorine, the outer layer K+ purple as in the cortex; disk dark orange-red; hypothecium hyaline, oil-droplet-inspersed, slowly 1+ blue; hymenium 85-90 µm, hyaline, 1+ blue, with the upper ca. 25 µm dark with yellow granules and K+ purple; spores 8, ellipsoid, polarilocular, 11-18 X 7-11 µm, septum 6-7 µm.

This species grows on old wood and barks. Although it is primarily a boreal forest species, a specimen from Arizona is in WIS.

If not the same as C. chrysophthalma Degel., this is certainly very closely related and perhaps a vicarious species. J. Santesson (1970) lists C. discolor as having the anthraquinones emodin, parietin, 2-chloroemodin, and fragilin, while C. chrysophthalma has the same except for lacking the 2-chloroemodin. As these results are based on single or two-specimen samples, the possible variation is not known. Descriptions suggest that the apothecia differ in the yellower color of the disk of C. chrysophthalma, and its lack of oil in the hypothecium, as well as its thinner margin. However, the majority of specimens lack apothecia, and the sterile thalli do not appear to differ. My earlier determinations of C. epiphyta from the Keele River region collected by Scotter (Bird et al. 1981) should be corrected to this species.