Arthonia didyma Arthoniaceae
Arthonia didyma

Growth type crustose. Photobiont Trentepohlia
Red-brown pigment K+ grey or olive. Epithecium, hymenium and sometimes hypothecium with orange-red K+ purple-violet pigment

Smooth bark of shrubs and trees (often Corylus) in unpolluted woodlands

Thallus +/- inconspicuous, pale brownish or olive-grey. Small, flat, brown or black apothecia, irregular, rounded or shortly linear. Spores are 1-septate, 14-17 x 4.5-7 Ám, colourless then becoming brownish and warted. Pycnidia are rare. Micrographs below.

Arthonia spadicea has larger apothecia and smaller spores. A. muscigena (now Bryostigma lapidicola), photobiont chlorococcoid, narrower spores


Arthonia didyma

Arthonia didyma

Arthonia didyma

Micrographs
Arthonia didyma, spores

Arthonia didyma, spores

Arthonia didyma, spores
Arthonia didyma
Brands Bay and Broadstone, Dorset. January 2013, March 2020, January 2024

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