Ergot is a plant disease caused by the fungus Claviceps purpurea, which infects the developing grains of cereals and grasses. Ergot symptoms become evident during kernel formation, when ergot bodies, compact masses of fungal mycelium also known as sclerotia, are produced instead of normal grain. Crops such as rye and some grasses are more susceptible to ergot infection because they are open-pollinated, allowing easy access of the fungus into the flowering head. Grains such as wheat and barley are less likely to become infected because they are self-pollinated, but may still develop levels that result in downgrading. Oats are seldom affected. Ergot poisoning occurs when a person ingests ergots, which are grains that contain the C. purpurea fungus. The fungus turns the grain hard and dark in color. Symptoms of ergot poisoning can be neurological, gastrointestinal, or cardiovascular.