Sclerotium

Sclerotium, a densely-compacted tuberous form of mycelium which occurs in many groups of Fungi as a resting stage and store of reserve material. It consists of a central medullary tissue, often pseudoparenchymatous, enclosed by one or more layers of thick-walled cortical cells. The best-known example is that of the pyrenomycetous Claviceps purpurea, which is the ergot (q.v.) of grasses.