Mushrooms

Mushrooms are the fruiting bodies of certain species of higher fungi. The vegetative tissues of these fungi consists of immense lengths of microscopic, thread-like hyphae, and their aggregations known as mycelium, which grow in surface soils, organic debris, and in association with plant roots.

Strictly speaking, a mushroom is the sporulating or fruiting body of a fungus in the division Basidiomycetes, a large and diverse group of about 16,000 species, sometimes known as club fungi. Species of Basidiomycetes can be saprophytic, parasitic, or mycorrhizal in their ecology. Because of the relative complexity of their anatomy and breeding systems, the Basidiomycetes are considered to be the most evolutionarily advanced of the fungi. The mushrooms of these fungi are technically known as basidiocarps. These structures are formed of specialized mycelium, and are the spore-producing stage of development. The basidiocarp is a relatively short-lived stage of the life cycle, most of which is spent living as microscopic, thread-like hyphae, which ramify extensively through the growth substrate of the fungus.

However, in its common usage, the word mushroom is also used to refer to the spore-producing bodies of other types of fungi, in particular a few species in the division Ascomycetes or sac fungi, which includes the familiar, edible morels and truffles. Some of the non-Basidiomycetes species that develop "mushrooms" are also discussed in this entry.

Mushrooms have long been avidly sought-after as a tasty country food in many cultures, although some peoples, notably the Anglo-Saxons of Britain, have tended to disdain these foods. This has not been because of the flavor of mushrooms, but rather because some species are deadly poisonous, and these are not always easily distinguished from nontoxic and therefore edible species.

The mycophobia (that is, fear of fungus) common to some people and cultures can be illustrated in many ways, including the derivation of the word "toadstool," a commonly used name for mushrooms that have an erect stalk and a wide cap. "Tod" is the German word for death, and the deadly, poisonous nature of certain mushrooms may be the likely origin of the word toadstool. The etymology of toadstool is further compounded by the poisonous nature of toads. In any event, European folk tales refer to toadstools as places where poisonous toads sit on poisonous mushrooms in the forest, a myth perpetuated in whimsical drawings accompanying fairy tales and other stories intended for children.

Mushrooms have many fascinating properties, in addition to the extreme toxicity of some species. Mushrooms can sometimes grow extremely rapidly—in some cases, masses of mushrooms can seemingly appear overnight, under suitable environmental conditions, and usually following a heavy rainfall. Mushrooms may also have unusual shapes and growth patterns, for example, the concentric circles or "fairy rings" that some species develop in open places, such as fields and meadows. These and other interesting qualities were not easily explainable by naturalists in earlier times. As a result, mushrooms have acquired a supernatural reputation in some cultures, and are commonly associated with cold, dank, dangerous, or evil contexts. Many cultures have similarly regarded a few other creatures, such as snakes, bats, and spiders. Today, however, these various cultural prejudices are much less prevalent, because we have a greater scientific understanding of the biology and ecology of mushrooms and other unusual organisms.