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Verrucaria dacryodes Nyl.
Family: Verrucariaceae
Verrucaria dacryodes image
Othmar Breuss  
Thallus: regularly areolate with fine fissures, thinning at margin, 0.15 -0.25 mm thick, forming patches up to 13 mm across, without a prothallus areoles: subangular, flat, 0.2-0.3 mm wide surface: brownish gray to brown, dull, rough anatomy: subparaplectenchymatous throughout, composed of small cells, above with a single layer of brownish cells; algal layer: 70-100 µm thick, with algal cells 5-9 µm in diam.; basal layer: brown to brown-black but not carbonaceous, discontinuous, subparaplectenchymatous, composed of roundish angular cells 6-9 µm in diam, with substrate fragments. Perithecia: arising from between the areoles, scarcely emergent over surface level of thallus, with flattened or slightly convex apices; exciple: subglobose, 0.15-0.20 mm wide, brown; involucrellum: contiguous with exciple, comparatively thick (40-50 µm), extending down to base of exciple and slightly incurved beneath, but basal part usually weakly delimited as merging with brown-black basal layer; periphyses c. 20 µm long, simple asci: clavate, 45-55 x 13-18 µm, 8-spored ascospores: hyaline, simple, tear-shaped, 12-16 x 5-7 µm Pycnidia: unknown Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: epilithic, on calciferous sandstone World and Sonoran distribution: endemic in California. Notes: The major characteristics of Verrucaria dacryodes are the areolate thallus, small perithecia that are clasped by a comparatively thick involucrellum and mostly situated between the areoles, and small tear-shaped spores. The marginal situation of the perithecia is not so clearly visible as in species of the Verrucaria lecideoides group as the fissures are very delicate. Small tear-shaped spores are also found in Verrucaria falcata, but this latter species is parasitic, has smaller thalli that lack a dark basal layer, and thinner involucrella. Verrucaria finkiana is superficially similar but has larger, subfusiform spores.