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Placidiopsis cinerascens (Nyl.) Breuss
Family: Verrucariaceae
Placidiopsis cinerascens image
André Aptroot  
Thallus: squamulose, 0.3-3 mm diam. squamules: 0.15-0.35 mm diam., 0.15-0.35 mm thick, discrete to contiguous or with margins slightly overlapping, flat or slightly convex, broadly attached to the substrate, roundish or incised-lobed upper surface: greenish gray to brownish, dull, naked or slightly grayish pruinose upper cortex: 15-25 µm, always overlain by an epinecral layer 10-30 µm medulla: white; algal layer: normally filling most of the thallus; algal-free medulla (in thick squamules): with many spherical cells 6-11 µm in diam. lower cortex: indistinct, composed of a few rows of more densely aggregated spherical cells; rhizohyphae: hyaline, 3-4 µm thick lower surface: pale, fastened by a loose rhizohyphal weft Perithecia: broadly pyriform to almost globose, up to 0.3 mm broad and ± bulging the lower side of squamules; exciple: colorless to yellowish, black around ostiolum; periphyses: 20-30 x 2.5-3 µm; apical cell: often slightly swollen (-4 µm) asci: oblong clavate, 55-65 x 11-16 µm, 8-spored ascospores: ellipsoid or ovoid, 2-celled, often slightly constricted at the septum, c. 15-19 x 6-7.5 µm Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: on ± calciferous soil on open places; Californian specimens are from serpentine soil World distribution: mediterranean Europe and Morocco, central Asia, SW North America and Mexico in mediterranean climates Sonoran distribution: Baja California.