Life habit: lichenized or not, lichenicolous (especially when young) or not Thallus: absent, endolithic, crustose, or squamulose, attached by the whole lower surface or basal end of squamule areoles/squamules: dispersed, adjacent, imbricate, or ascending, 2-10 mm wide, rounded to elongated or bullate, with entire, crenulate or lobed margin upper surface: from white to dark gray, green, or brown, sometimes rose or pale yellow, dull to shiny, epruinose to densely white pruinose, smooth to deeply fissured; vegetative dispersal units lacking upper cortex: varying from absent to 500 Ám thick, containing remnants of algae (chlor-zinc-iodine!), usually consisting of an upper epinecral layer and a lower stainable layer, the latter composed of thick- to rather thin-walled, anticlinally oriented hyphae with shortly thread-like, angular, or rounded lumina, often containing crystals of calcium oxalate, rarely lichen substances; algal layer: 30-100 Ám thick, horizontally continuous or rarely discontinuous medulla: white, of intricately interwoven hyphae, I-, often containing lichen substances and/or calcium oxalate photobiont: primary one a chlorococcoid alga, secondary photobiont absent, algal cells 10-15 Ám diam. lower cortex: poorly to well developed, composed of periclinally or anticlinally oriented hyphae, sometimes containing calcium oxalate lower surface: white to brown Ascomata: apothecial, laminal or marginal, sessile, with a constricted base, simple or rarely somewhat conglomerate, usually weakly concave to weakly convex and marginate when young, later often becoming more convex and immarginate, up to 5 (-10) mm diam., black, usually dull, epruinose or with white pruina of calcium oxalate; exciple: annular, composed of radiating, thick-walled, conglutinated hyphae with rounded to narrowly cylindrical lumina, varying from having a pale or colorless inner part and a darker gray, green, or brown rim, to being dark brown throughout; hypothecium: dark brown to colorless, composed of intricately interwoven hyphae, sometimes containing crystals of calcium oxalate, I-; epithecium: gray (K+ violet, N+ violet), green (K-, N+ violet or K+ violet/brown, N-), reddish brown (K+ red, N-), dull brown (K-, N-), or pale olivaceous brown to colorless (K-, N-) (pigments sometimes mixed), often containing crystals of calcium oxalate, rarely crystals of lichen substances; hymenium: hyaline, I+ blue, 50-80 micrometer high; paraphyses: straight, sparingly branched and anastomosing, not conglutinated, thin-walled, with an apical cell which is distinctly swollen and surrounded by a plus minus well developed gelatinous pigment cap or sometimes containing pigment in the cell wall asci: clavate, surrounded by a gelatinous, amyloid sheet, with a well developed, amyloid tholus containing a deeper amyloid, conical zone around the axial mass and a well developed, conical, often pointed ocular chamber (Bacidia-type), 8-spored ascospores: colorless, simple to 7 (-9) septate, broadly ellipsoid to acicular, smooth, without halo Conidiomata: pycnidial, laminal, immersed or partly protruding, with colorless or pale brown to black ostiole, with short, sparingly branched conidiophores conidia: acrogenous, filiform, curved Secondary metabolites: usually none, but in some species terpenoids, depsides, usnic acid, or fatty acids Geography: arctic to subtropical regions of the world, highest diversity in arid areas Substrate: soil and rock, often calciferous. Notes: Many species start their development on the thallus of other lichens. Some remain lichenicolous, but others become autonomous. The hosts referred to below may be visible only at an early stage, and may even be facultative in some species. Only a few secondary metabolites have been identified in Toninia. Most are terpenoids, and some species and subspecies show diagnostic patterns on the chromatograms (see Timdal ).