Life habit: lichenized Thallus: immersed or rarely superficial and then thin, indistinct, dark grayish green, granular Apothecia: usually with a faint white pruina at least at edge (upper part) of exciple and below the capitulum, 0.5-1 mm tall, 4-9 times as high as the width of the stalk stalk: shiny black, 0.11-0.17 mm wide, consisting of blackish brown to dark aeruginose, irregularly interwoven and strongly sclerotized hyphae, becoming pale towards surface; outermost layer: paler and with a +distinct, gelatinous, hyaline coat capitulum: obovoid to lenticular, 0.23-0.34 mm in diam. exciple: dark brown to aeruginose, composed of elongated to almost isodiametric sclerotized hyphae, paler in outer part and +distinctly anticlinally arranged; hypothecium: dark brown with flat or slightly convex upper surface asci: cylindrical, 35-41 µm x 3.5-4.5 µm, with uniseriate spores ascospores: semi-mature spores: with a very irregular sulcate pattern (mainly longitudinally arranged ridges, which are disrupted by irregular cracks); mature spores: ellipsoid, 9-13 x 4-6.5 µm, with coarse irregular ornamentation of cracks and ridge fragments Pycnidia: frequent conidia: narrowly cylindrical, 4-5 x 0.8 µm Spot tests: thallus K+ dull yellow, C-, KC-, P-; apothecia I- Secondary metabolites: either none detected or sekikaic acid (major), 2-O -methylsekikaic acid (minor) and 4-O-methylhypoprotocetraric acid. Substrate and ecology: on old stumps or standing or fallen wood of coniferous and deciduous trees, more rarely on bark, often in exposed situations World distribution: northern boreal to temperate zones in North, Central and South America, and Australasia Sonoran distribution: southern California and Chihuahua. Notes: Calicium glaucellum is recognized by having rather short-stalked apothecia, the presence of a white rim along the edge of the exciple, the usually immersed thallus, and the medium-sized spores, which have an ornamentation of irregular ridges and cracks. It is very similar to C. abietinum but differs in having a white pruina on the lower side of the apothecium, at least at the edge of the exciple, black instead of brownish stalks and slightly smaller spores with a different spore ornamentation.