Arthonia atra grows on smooth bark of deciduous trees. It is known in coastal Norway from humid forests and woodlands north to Steinkjer in Trøndelag. Arthonia atra is characterized by lirellate apothecia with black margin and slit-like disc, an often mosaic forming silver-white thallus with trentepohlioid photobiont, and colorless, 3-septate spores without enlarged apical cell.
Arthonia atra
(Pers.) A. Schneid.
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Andreas Frisch
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NTNU Vitenskapsmuseet
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Håkon Holien
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NORD Universitet
