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Verrucaria beltraminiana (A. Massal.) Trevis.
Family: Verrucariaceae
Verrucaria beltraminiana image
Gerhard Neuwirth  
Thallus: deeply areolate, forming small patches or extensive thalli up to several centimeters across, up to 0.3 mm thick, margins thin, often bordered by a black, narrow or fimbriate prothallus areoles: angular, the steep side-walls brown or black, usually contiguous, plane, 0.2-0.8 mm wide surface: brownish gray, dull, grayish white pruinose, minutely wrinkled or roughened, thinly black-rimmed or not anatomy: upper cortex paraplectenchymatous, composed of a few layers of 4-6 µm in diam. cells, with a 10-20 µm thick amorphous epinecral layer, algal layer filling most of thallus, algal cells 6-12 µm in diam.; basal layer thin, brown to black (but not carbonaceous), composed of roundish-angular cells 5-7 µm in diam. with shortly filamentous, 4 µm thick hyphae Perithecia: numerous, situated at the margins of, or between the areoles, deeply immersed, with apices usually distinctly flattened and level with surface of the areoles; exciple: subglobose, 0.20-0.30 mm wide, c. 20 µm thick, dark; involucrellum: contiguous with exciple, extending to exciple base level and more or less incurved beneath, laterally c. 40 µm thick; periphyses 20-25 µm long asci: clavate, 60-85 x 20-28 µm, 8-spored ascospores: hyaline, simple, (rather broadly) ellipsoid, 17-22 x 7.5-9 µm Pycnidia: unknown Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: epilithic, on calcareous and siliceous rocks World distribution: Europe and Mexico Sonoran distribution: Baja California and southeastern Arizona. Notes: The areoles of the European type material are not black-rimmed and barely pruinose, and the perithecia have slightly emergent, convex apices, but there is some variation in these characters as is in the related Verrucaria lecideoides so that they seem to be of no taxonomic value. The differences against the latter species given in the literature is confusing (compare Zschacke 1934, Wirth 1995, McCarthy 1994). Spore sizes and perithecium dimensions seem to be the only constant and reliable features to distinguish these species: In Verrucaria beltraminiana the spores (17-22 x 7.5-9 µm versus 12-15 x 5-7 µm) and perithecia (exciple 0.20-0.30 mm versus 0.15-0.22 mm) are significantly larger than in V. lecideoides.