Mycelium, the vegetative part of a fungu , serving the same physiological purposes as loots in attaching the plant to its substratum and in taking in nutriment. Its typical form is that of branching filaments (hyphce), with or without transverse partitions, sometimes in parasitic forms, putting out minute sucker-like branches (hauslona) which penetrate the cells of living host-plants Resting reserve-stores resembling tubers, and known as sclerotia, with thickened external walls, occur on some mycelia, as in ergot (q.v.). In other cases, such as Acjaricus melleus, thick mycelial strands, or "sclerotia with growing points" are formed, which are known as Rhizomorpha, and in this particular species ramify beneath the bark of the pine tree, the mushroom-like fructification being perhaps several feet distant from the tree. Another dense mvcelial structure, known as mycorhiza, occurs in the truffle Elaphomyces, and other fungi, round the roots of various trees, including conifers and Cupuliferaj. This mycorhiza prevents the formation by the tree of its normal root-hairs, and is believed by Frank to be in a condition of symbiosis (q.v.) with the tree, performing for it the function of absorption otherwise carried on by root-hairs. In the cultivation of the mushroom the mycelium is popularly termed "spawn."