Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Thallus: crustose, areolate, up to 100 mm in diam. and up to 0.7 mm thick; prothallus: black to gray, obvious between the areoles and at the thallus margin areoles: +angular, plane to concave, 0.5-0.7(-1.2) mm wide surface: brown, smooth, lacking asexual propagules cortex: upper cell layer brown to pale brown, 20-50 µm thick, with hyphae 3-4.5 µm thick, with a thick (35-95 µm) epinecral layer medulla: I+ violet; algal layer: 65-120 µm thick; algae: 9-11(-15) µm in diam. Apothecia: dark gray to black, dull, immersed, round to angular, 0.6-0.8(-1.3) mm in diam. disc: dark gray to black, dull, plane to concave, pruinose or not margin: gray or black, dull, at first usually not distinct, later vanishing exciple: ectal zone dark brown to gray, inner zone hyaline to brown, 15-30 µm thick or completely reduced, K- epithecium: black-brown to green-brown, 10-20 µm thick hymenium: hyaline, I+ yellow to bluish, I± orange-red, 70-125 µm tall; subhymenium: hyaline to brown, 30-120 µm thick; hypothecium: dark to pale brown or nearly hyaline, up to 200 µm thick ascospores: hyaline, simple, ellipsoid, 13-19.5(-24) x (6)7-9.5(-13) µm Pycnidia: immersed conidia: cylindrical, 6-9(-12) x 1-1.2(-1.5) µm Spot tests: upper cortex: K-, C-, KC-, P-; medulla: K-, C-, KC-, P- Secondary metabolites: confluentic acid, 2'-O-methylperlatolic acid, 2'-O methylmicrophyllinic acid. Substrate and ecology: exposed, on non-calciferous rock, rarely on lichens World distribution: Africa, Asia, Australia, Europe, and North America Sonoran distribution: Arizona at high elevations. Notes: Immersaria athroocarpa is characterized by nitid brown thallus areoles with a +concave surface and a rather thick epinecral layer, constantly immersed, black apothecia, and large ascospores. The species is very variable with regard to its hypothecial pigmentation. From species of Lecidea with a brown thallus, it is distinguished by its Porpidia-type asci. The very common Lecidea atrobrunnea is superficially similar but usually has much more robust areoles.