Claviceps purpurea is a fungus that primarily infects rye and other grasses. It produces dark, elongated structures called sclerotia, which replace the grain in infected plants. These sclerotia contain alkaloids that can be toxic to humans and animals if consumed. This fungus is historically significant because it is associated with ergotism, a condition caused by the ingestion of contaminated grains. Symptoms of ergotism can include hallucinations, convulsions, and gangrene. Claviceps purpurea has also been studied for its potential medicinal properties, particularly in the development of ergotamine, a drug used to treat migraines.