The visible part of any fungus, the mushroom or toadstool, is called the fruiting body, and is the means by which the fungus releases its spores. Except in tropical climates, the fungus itself cannot live in the open air, and it lives underground or within the body of another organism such as a tree or other plant. Fungi are not plants. They belong to a kingdom of their own and cannot manufacture their own food through photosynthesis. They spread by way of mycelia, fine root-like threads which are difficult to find and almost impossible to distinguish as individual species. These mycelia enable the fungus to obtain nourishment by dissolving the tissue of plants, living or dead. Some can even dissolve metal and plastic. Many fungi including the Boletaceae, grow around the roots of living plants including trees. This has the effect of extending the plant's root system over a wide area, enhancing the plant's uptake of water and minerals. The fungus benefits by absorbing organic compounds from around the plant's roots. These fungi are often essential for the plant's survival. The Devil's bolete appears in late summer and early autumn. It is a colourful species, which carries more than one surprise. If cut in half, the creamy flesh turns sky-blue. Its discoverer, an Austrian, claimed to be ill for days after he had first smelled it. This, together with its reputation for deadliness, convinced him that the fungus must have been the work of the devil himself.