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Verrucaria acrotella Ach.
Family: Verrucariaceae
Verrucaria acrotella image
Othmar Breuss  
Thallus: superficial, variable, uneven verrucose or granular to irregularly rimose-areolate, continuous or broken up, 0.07-0.20 mm thick, somewhat subgelatinous when wet, partly delimited by a thin brown fimbriate prothallus areoles: subangular to irregular, flat, 0.3-0.5(-1) mm wide, sometimes widely separated or in small groups, but margins often slightly elevated and irregularly outlined surface: brown, dull anatomy: upper cortex indiscernible, thallus 70-200 µm thick, with algal cells 6-10 µm in diam. dispersed throughout most of the thallus; mycobiont portion: subparaplectenchymatous, composed of cells 5-8 µm in diam. Perithecia: 1-3 per areole, immersed in the thallus with upper third protruding, subglobose; exciple: brown, 0.20-0.23 mm wide, c. 10 µm thick; involucrellum: extending to exciple base level and slightly incurved beneath, broadening to 40-60 µm thick at base; periphyses c. 20 µm long and 2.5-4 µm thick asci: clavate, 8-spored ascospores: hyaline, simple, ellipsoid , 12-17 x 7.5-9 µm Pycnidia: unknown Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: epilithic, on granitic rocks World distribution: Europe and North America Sonoran distribution: found twice in southern California (San Diego County). Notes: Verrucaria acrotella is similar to V. memnonia, but the latter species has narrower spores and an involucrellum which is not incurved basally.