Life habit: lichenized Thallus: crustose, areolate, without elongated lobes; prothallus: absent surface: gray to blue-gray, smooth, isidiate, sorediate or lobulate soredia: (if present) granular, bluish, in irregular soralia isidia: (if present) short globular to subsorediate cortex: cellular, thick or thin, without granules Apothecia: rare, adnate, 0.3-0.8 mm in diam., lecanorine disc: orange, flat, epruinose margin: persistent, flush or raised; thalline margin present, concolorous with thallus; proper margin not visible parathecium: cellular (paraplectenchymatous); exciple below hypothecium prosoplectenchymatous epihymenium: golden, K+ red, H-, 10%N-, cN-, C- hymenium: hyaline, 55-70 µm tall paraphyses: 1-2 tip cells swollen, not branched or with few branches; subhymenium hyaline asci: cylindrical, 8-spored ascospores: hyaline, 2 locules, ellipsoid, 11-14 x 5.5-7 µm, isthmus 3.5-5.5 µm, spore end wall thin Pycnidia: not observed Spot tests: apothecial margin K+ violet, H+ violet, 10% N+ violet, cN+ violet, C+ violet; thallus K+ violet, H+ violet, 10%N+ violet, cN+ violet, C+ violet Secondary metabolites: thalloidima green, parietin, fallacinal, emodin, teloschistin, and parietinic acid. Substrate and ecology: on bark or on non-calcareous or calcareous rocks World distribution: Europe and North America Sonoran distribution: eastern and southern Arizona. Notes: The thallus of Caloplaca chlorina is quite variable but usually has isidia and lobules and only occasionally produces slightly bluish true soredia. The collections from bark usually have true soredia while those on rock usually have isidia or lobules. The apothecial margin has no excipular ring as in C. sideritis and that also lacks isidia and lobules. Caloplaca cerina is similar but only occurs on bark and wood.