Physciaceae Rinodina roboris Growth type crustose Chemical results: K+ yellow On rough, well-lit bark of Oak, Ash and Beech. Can be locally common in parts of southern Britain. Thick pale grey or grey-green thallus, often irregularly cracked. Apothecia with thick margins, the discs dark brown to black. Spores brown, 1-septate, 14-22 x 8-12 µm with rounded locules. Microscope photograph below. Similar: Rinodina sophodes is K- and usually found on the twigs and branches of smooth-barked trees

Microscope photograph

Rinodina roboris
On old Oak. Holton Lee, Dorset. October 2012