Opegrapha atra Roccellaceae
Opegrapha atra

Growth type crustose
Chemical results: Thallus negative. Exciple K+ olive-green.
Hymenium I+ blue, epithecium brown or green-brown, K+ olive-green.

Common on smooth, shaded trunks, branches and twigs, rare on wood. Forms extensive mosaics on young trees but tends to avoid nutrient-enriched bark.

Short (1mm) prominent lirellae with central slit, often densely crowded at centre of thin or +/- evanescent thallus. Pycnidia rare. Spores 3-septate, 13-18(-20) x 2.5-4(-5) Ám. Microscope photograph below.


Opegrapha atra


Opegrapha atra

Microscope photograph
Opegrapha atra
Opegrapha atra
On Sycamore. Kimmeridge, Dorset. January 2013

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