Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.

Thallus: continuous to sparingly and irregularly rimose, filmy, subgelatinous when wet, usually hardly more than 0.05 mm thick, with or without a very thin black basal layer, without an apparent prothallus surface: green or grayish green to brownish gray or brown, smooth anatomy: paraplectenchymatous throughout, with a single layer of pigmented cells above, with algal cells 5-12 µm in diam. filling the whole thallus Perithecia: immersed in low swellings of the thallus with the apical portion more or less bare; exciple: subglobose to slightly applanate, colorless to pale brown, 0.15-0.20 mm wide; involucrellum: c. 20-30 µm thick, spreading laterally into the thallus, extending down to exciple-base level, of "Zellnetztyp" with colorless tissue between involucrellum and exciple; periphyses 20-30 µm long asci: clavate, 8-spored ascospores: hyaline, simple, ellipsoid, 18-25 x 7.5-12 µm Pycnidia: unknown Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: epilithic, on siliceous rocks in or by streams, also on flushed or damp rocks in shaded places, montane World distribution: northern Eurasia, North America, south-eastern Australia, New Guinea, and New Zealand Sonoran distribution: Arizona (Apache, Gila, and Pima Counties) and southern California (Los Angeles County). Notes: Among the amphibious species, Verrucaria hydrela is characterized by a thin, generally uncracked thallus, a thin and usually wide spreading involucrellum and comparatively small spores.