ergot A fungus that grows on grasses and cereal grains; the ergot of medical importance is Claviceps purpurea, which grows on rye. The consumption of infected rye is harmful, causing the disease known as St Anthony's fire (ergotism), and can be fatal. The first connection with infected rye (spurred rye, so‐called because the grain heads of infected rye appear spurred) was recorded by physicians in Marbourg (France) in 1597.

The active principles in ergot are alkaloids (ergotinine, ergotoxine, ergotamine, ergometrine, etc.), which yield lysergic acid on hydrolysis. Its effect is to increase the tone and contraction of smooth muscle, particularly of the pregnant uterus. For this reason ergot has been used in obstetrics.

ergot The dark hard-walled mass of hyphae produced by the fungus Claviceps purpurea (see Ascomycota) in the grain of the cereals and other grasses that it parasitizes. Ergots are the sclerotia of this species – resting bodies that germinate in favourable conditions to produce mycelia or ascocarps. They contain alkaloids related to LSD, which cause blood vessels to constrict and are used therapeutically in the treatment of migraine and haemorrhage. Ingestion of infected grain can result in ergot poisoning (ergotism), with symptoms of gangrene and hallucinations – known as `St Anthony's fire' in the Middle Ages.

ergot A disease that affects many grasses, including cereals. It is caused by the fungus Claviceps purpurea; the conspicuous, hard, black sclerotia of the fungus replace the grain in the spikelets of an infected plant. These sclerotia contain alkaloids which can cause severe poisoning or even death if ingested by animals or humans.

ergot(St Anthony's fire) A disease which affects many grasses, including cereals. It is caused by the fungus Claviceps purpurea; the conspicuous, hard, black sclerotia of the fungus replace the grain in the spikelets of an infected plant. These sclerotia contain alkaloids which can cause severe poisoning or even death if ingested by humans or other animals.

ergot (er-got) n. a fungus (Claviceps purpurea) that grows on rye. It produces several important alkaloids, including ergotamine and ergometrine. See also ergotism.