According to Fungi of Great Britain and Ireland: "Stromata developing in upper surface of living leaves, 0.5–2.0 mm diam and 120–220 µm tall, irregularly shaped but typically ± circular, shallowly domed or ± flat-topped, subcuticular, shining black, scattered or gregarious, composed of ± vertically arranged thick-walled polygonal cells, dark brown in the central part and with 2-3 more strongly pigmented layers of cells at the surface."