This is a lichen everyone will have seen but only those with a particular interest will have taken any notice of or given any thought to! Not only is it totally insignificant to look at it has a very difficult name to say, let alone remember, it is Lecanora conizaeoides. This lichen does not look like anything other than some boring, crusty, possibly mouldy skin but it is, indeed, a lichen and is probably our most common lichen at that. It can be found primarily on tree bark and it is probably most notable on oak trees; there can hardly be an oak tree in Dorset that does not bear some of this lichen on it somewhere. It does also occur on walls, rocks and even soil. This was once a quite rare species but during the course of the twentieth century it became one of the most common as it is totally impervious to sulphur dioxide and so thrives in polluted areas where it has replaced other lichen that have dwindled.
The Nature of dorset 