Produced by a lower fungus (Claviceps purpurea), grows parasitically on rye and, to a lesser extent, on other species of grain and on wild grasses. Kernels infested with this fungus develop into light-brown to violet-brown curved pegs (sclerotia) that push forth from the husk in place of normal grains. Ergot of rye (Secale cornutum) is the variety used medicinally.