Mycoblastus caesius (Coppins & P. James) Tønsberg

Sommerfeltia, 14: 222, 1992. Basionym: Haematomma caesium Coppins & P. James - Lichenologist, 10: 200, 1978
Description: Thallus crustose, endosubstratic or thinly episubstratic in non-sorediate parts, effuse and up to 5(-10) cm wide or forming small, poorly delimited patches, pale grey, continuous or with scattered, c. 0.5 mm wide areoles, delimited by a thin, dark blue-grey prothalline line, sorediate; soralia maculiform, discrete to finally confluent, 0.2-1 mm across, blue-grey to rarely whitish, the soredia c. (20-)30-70(-100) µm in diam., the external hyphae often blue-grey, N+ violet. Apothecia extremely rare (not known from European material), biatorine, black, scattered, with a convex, epruinose disc, without a distinct proper margin. Proper exciple much reduced laterally, the hyphae vertically arranged and resembling paraphyses, merging with epithecium; epithecium indigo-blue to greenish, sometimes with a brownish tinge, K+ intensifying green-blue; hymenium colourless, inspersed with granules; paraphyses branched and anastomosing. Asci 2-spored, cylindrical-clavate, thick-walled, the apical dome K/I+ blue, with a distinct ocular chamber, the outer layer thickenend and forming a K/I+ dark blue apical cap. Ascospores 1-celled, hyaline, ellipsoid, 50-57 x 27-36 μm, the wall 4-7 μm thick. Photobiont chlorococoid. Spot tests: K-, C-, KC-, P-, UV+ white. Chemistry: perlatolic acid.
Note: on the acidic smooth bark of deciduous trees, rarely on conifers; widespread in western Europe, with only a few records from the montane belt of the Alps (Austria, Switzerland). To be looked for in the Italian Alps.
Growth form: Crustose
Substrata: bark
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)

pH of the substrata:


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Altitudinal distribution:


Predictive model

P.L. Nimis CC BY-SA 4.0
TSB 16760

P.L. Nimis; Owner: Department of Life Sciences, University of Trieste
Herbarium: TSB (16760)