Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.
Thallus: rimose to areolate, continuous or broken up, moderately thick (0.2-0.3 mm), with subacute or blunt fissures, lacking a black basal layer (but medulla sometimes brown in lower zone), with or without a narrow black prothallus areoles: angular to irregular in outline, dull, plane, 0.2-0.5 mm wide, marginal and fertile ones up to 0.8 mm wide, in parts secondarily subdivided into smaler units surface: brown, dull, smooth anatomy: upper cortex: poorly defined, composed of 1-3 layers of cells 4-6 µm in diam., with a brown uppermost cell layer; algal layer: 80-150 µm thick, with algal cells 5-12 µm in diam., mycobiont paraplectenchymatous, with cells 4-8 µm in diam..; medulla: subparaplectenchymatous, colorless or patchily brown, especially around perithecia, or pale brown in lowermost zone, interspersed with substrate fragments and crystals Perithecia: one per areole, ±centrally immersed with only the tip slightly protruding to hemispherically prominent without thalline covering; exciple: subglobose to broadly pyriform, 0.2-0.3 mm wide, colorless to dark brown, 15-20 µm thick; involucrellum: extending to exciple-base level, broadening to 80-100 µm thick at the base, contiguous with exciple; periphyses 25-35 µm long, thin, simple asci: clavate, 65-70 x 25-30 µm, 8-spored ascospores: hyaline, simple, ellipsoid, 17-23 x 8-10 µm Pycnidia: unknown Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: epilithic, on both acid and carbonate rocks, montane World distribution: Europe and North America Sonoran distribution: apparently not rare in Arizona (Cochise, Coconino, Pima, and Navajo Counties) and also known from California (Los Angeles County). Notes: The segregation of Verrucaria nigrofusca from V. fuscoatroides is retained with some hesitation as it is based mainly on the smaller, especially narrower spores of the former. Moreover, in Verrucaria fuscoatroides the perithecia tend to be larger (exciples up to 0.4 mm wide). Verrucaria endocarpoides also has somewhat larger spores, and is further distinguished by immersed perithecia and shorter and thicker periphyses.