a diseased condition of rye and other cereals, in which the grains become black, and often spur-shaped. it is caused by a parasitic fungus, claviceps purpurea.-the mycelium or spawn of this fungus infecting grains of rye and wheat. it is a powerful remedial agent, and also a dangerous poison, and is used as a means of hastening childbirth, and to arrest bleeding.-a stub, like soft horn, about the size of a chestnut, situated behind and below the pastern joint.-see 2d calcar, 3 (b).