Arthonia didyma Arthoniaceae
Arthonia didyma

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

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

Immmersed thallus with small, flat, brown or black apothecia. Spores are 1-septate, 14-17 x 4.5-7 Ám, colourless becoming brown. Pycnidia rare. Microscope photograph below.

Similar: A. spadicea can appear similar but has larger apothecia and spores

Arthonia didyma

Microscope photograph
Arthonia didyma, spores
Arthonia didyma
Brands Bay, Dorset. January 2013

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