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Verrucaria amylacea Hepp
Family: Verrucariaceae
Verrucaria amylacea image
Othmar Breuss  
Thallus: diffuse, indistinct or almost absent, thin or rarely thick (up to 0.1-0.2 mm), irregularly and sparsely fissured to continuous and imperfectly areolate surface: white or gray to pale brown, sometimes with tiny brown dots, smooth or rough, dull anatomy: upper cortex scarcely distinguishable as a thin paraplectenchyma of small cells 3-5 µm in diam., diffusely delimited from the algal layer, with algal cells up to 10 µm in diam. forming an irregular layer intermixed with tiny substrate particles Perithecia: on thin thalli hemispherical emergent, their bases sometimes narrowly covered by a thin thalline layer, semi-immersed in thicker thalli; exciple: 0.2-0.3 mm wide, subglobose, colorless to brown; involucrellum: appressed to the exciple, extending down to exciple-base level, 50-70 µm thick, rather even in thickness; periphyses 20-25 µm long asci: clavate, 8-spored ascospores: hyaline, simple, ellipsoid , 14-20 x 7-9 µm Pycnidia: unknown Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: endolithic to thinly epilithic, on calcareous or at least superficially calciferous rocks World distribution: central Europe and North America Sonoran distribution: Arizona and southern California. Notes: Thallus development and spore size is similar to Verrucaria floerkeana, but this latter species has a thinner involucrellum.