Claviceps purpurea, Ergot. In Guernsey this fungus has only been found growig on Marram Grass, where in some years it is quite common. In the winter the mature fungus drops to the ground and in spring it produces fruit bodies resembling minute mushrooms that produce spores that infect the female flowers of the Marram. It is deadly poisonous. In the past this fungus growing on Rye contaminated bread . The disease this produces in humans is called Ergotism or St Anthony's Fire (after the monks who used to specialise in treating it). The poison constricts the blood vessels leading to great pain in the limbs and sometimes gangrene.