Fungal mycelium in the soil of a pot-grown lime tree. The picture shows the soil profile at the edge of a shallow tray containing a small leaved lime, Tilea cordata, grown as a bonsai. The upper surface is moss-covered, with scattered fungal fruiting bodies. Within the soil (below), the roots of the tree appear as branched brown filaments. These roots are in intimate contact with the mycelium of the fungus, seen as a mass of very fine white threads - the hyphae. Fungal mycelium permeates fertile soils worldwide. This tree was transplanted to a pot from open ground in a garden 20 years ago. Such "mycorrhizal" relationships between mycelium and tree roots are widespread and symbiotic. Trees gain access to minerals and water over a wider area; the fungi gain products of photosynthesis. In woodland, trees are interconnected by mycelial networks; the so-called "Wood Wide Web"