Rhizocarpaceae Rhizocarpon oederi Growth type crustose Chemical results negative. Epithecium olive to dark green Usually an upland species on exposed, iron-rich rocks, often associated with mines or quarries. Patches of areolate or rimose orange or rusty-red thallus with black umbonate or gyrose apothecia. The spores are colourless, 3-septate. Similar: Tremolechia atrata and Lecidea lithophila

Rhizocarpon oederi
On ironstone. Studland Heath, Dorset. May 2015