Aspicilia grisea, occupying the right side of the image, with Porpidia tuberculosa to the left. Growing on the top of a sandstone gravestone, VC 27, E. Norfolk. This material, like much from lowland England gives only a K+ yellow reaction (not K+ yellow to red). This does not appear to be due to a low concentration of norstictic acid (no red crystals are produced with K in a microscope preparation) but rather due to a slightly different chemistry (perhaps stictic acid?).