TYPE Unclear. Original description of basionym Coniangium caesium Flot. in Körber (1855) cites “Exs. Fw. LE. 117 A. B.”
Description. Lichenized fungus.
Thallus crustose, granular, whitish to greyish-green or yellowish; vegetative diaspores absent; prothallus not seen. Photobiont chlorococcoid alga. Ascomata arthonioid (margin lacking), roundish, immersed to sessile, 0.2-0.7 mm diam, frequent. Disk flat to slightly convex, dark brown to black, densely bluish-grey pruinose; exciple poorly developed, very thin, reddish brown; epithecium reddish brown, ~10 μm thick; hymenium colorless to yellow-brown, 60-75 μm high; hypothecium dark-red-brown, conical up to 60 μm high; paraphysoids thin, sparingly branched, tips not or only slightly thickened. Asci broadly clavate to subglobose, approaching Arthonia-type, 8-spored. Ascospores colorless, bacilliform, 3-septate, constricted at septa, 15-20 x 4-6 μm. Pycnidia absent.
Chemistry. Spot tests UV-, K- or K+ pale yellow, C-, KC- or KC+ pale yellow, PD-; secondary metabolites: usnic acid, possibly zeorin.
Substrate and Habitat. On exposed bark near water.
Distribution. Eastern North America and Europe; in North Carolina throughout.
Notes. This species was formerly known as Arthonia caesia, but molecular analysis found it to belong in the yellow leprose genus Chrysothrix (Ertz & Tehler 2011).
Brodo, I.M., S. Duran Sharnoff & S. Sharnoff. (2001) Lichens of North America. Yale University Press, New Haven & London. 795 pp.
Ertz, D. & A. Tehler. (2011) The phylogeny of Arthoniales (Pezizomycotina) inferred from nucLSU and RPB2 sequences. Fungal Diversity49(1): 47-71.
Körber, G.W. (1855) Systema Lichenum Germaniae (I-XXXIV). Die Flechten Deutschlands mikroscopisch geprüft, kritisch gesichtet, charakteristisch beschrieben und systematisch geordnet (original description as Leprantha caesia).
Nimis P.L. (2016) ITALIC - The Information System on Italian Lichens. Version 5.0. University of Trieste, Dept. of Biology, (http://dryades.units.it/italic), accessed on 2022-06-03.