Fungi, Food, Poison and Mystery

General Practitioner (Rtd.), Westbury-on-Trym When we speak, loosely, of the structures we call mushrooms and toadstools, we refer to the fruiting bodies of fungi. Fungi, unlike green plants which absorb carbon dioxide from the air, obtain their nutrients by breaking down the tissues of wood, leaves, roots or, occasionally, animals, either living or dead. Essentially, fungi consist of ramifying threads or hyphae and these, together, form the mycelium; when two mycelial groups conjugate under the correct climatic conditions, then fruiting bodies are formed. It is the fruiting body which liberates the spores of the fungus. Each spore contains a single cell and one reproductive body produces them in their millions. In contrast, a seed of a green plant contains a complete embryo. Fungi play an important part in the decay of dead vegetable material; but for fungi, our forests would appear very different places. Fungi are also important, in association, in stimulating the optimal growth of certain plants; thus, it has been shown that fungi must be present in the soil if various orchids are to grow successfully. Again, there seems no doubt that some conifer species are more healthy when they produce particular short roots whose function appears to be entirely that of fungal association; Scots pine Pinus sy/vestris is an example here. Fungal spores are produced in two ways. Firstly, in the Ascomycetes, the most abundant yet least conspicuous group, the spores are formed in a club-shaped body, the ascus and, when mature, these spores are shot out in their dispersal. Basidiomycetes include the most spectacular and well-known fungi; in this group, the spores mature from projections at the top and, subsequently, outside the basidial cells. These spores are just dropped when fully developed. While identification of the fruiting body must depend, in the ordinary way, on macroscopic characteristics, microscopic examination of the spores is necessary in some cases for exact classification. Depending on the species, fungal spores may be ovoid, elliptical, polygonal, round or other different forms. In addition, spores of some species show warts orspines which may be separate orconnected by lines. More simply, in the case of the larger brackets or agarics, spore prints can be obtained and will give valuable information. The fungal cap is placed on paper, gills downwards, for a few hours when a print derived from the dropped spores will have resulted. Naturally, if a black or brown print is expected, …