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A mushroom is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground on soil or another food source. A toadstool generally refers to a poisonous mushroom.
The standard for the name "mushroom" is the cultivated white button mushroom, Agaricus bisporus; hence, the word "mushroom" is most often applied to those fungi (Basidiomycota, Agaricomycetes) that have a stem (stipe), a cap (pileus), and gills (lamellae, sing. lamella) on the underside of the cap. "Mushroom" also describes a variety of other gilled fungi, with or without stems; therefore the term is used to describe the fleshy fruiting bodies of some Ascomycota. The gills produce microscopic spores which help the fungus spread across the ground or its occupant surface.
Forms deviating from the standard morphology usually have more specific names, such as "bolete", "truffle", "puffball", "stinkhorn", and "morel", and gilled mushrooms themselves are often called "" in reference to their similarity to Agaricus or their order Agaricales.
The term "mushroom" and its variations may have been derived from the French word Calocybe gambosa in reference to moss ( mousse). Delineation between Edible mushroom and poisonous fungi is not clear-cut, so a "mushroom" may be edible, poisonous, or unpalatable. The word toadstool appeared first in 14th-century England as a reference for a "stool" for , possibly implying an inedible poisonous fungus, an association it carries in modern terminology.
While modern identification of mushrooms is quickly becoming molecular, the standard methods for identification are still used by most and have developed into a fine art harking back to medieval times and the Victorian era, combined with microscopic examination. The presence of juices upon breaking, bruising-reactions, odors, tastes, shades of color, habitat, habit, and season are all considered by both amateur and professional mycologists. Tasting and smelling mushrooms carries its own hazards because of poisons and . are also used for some genera.Ammirati et al., pp. 40–41.
In general, identification to genus can often be accomplished in the field using a local field guide. Identification to species, however, requires more effort. A mushroom develops from a button stage into a mature structure, and only the latter can provide certain characteristics needed for the identification of the species. However, over-mature specimens lose features and cease producing spores. Many novices have mistaken humid water marks on paper for white spore prints, or discolored paper from oozing liquids on lamella edges for colored spored prints.
Within the main body of mushrooms, in the Agaricales, are common fungi like the common fairy-ring mushroom, shiitake, enoki, oyster mushrooms, and other , magic mushrooms like species of Psilocybe, Volvariella, Coprinus comatus, etc.
An atypical mushroom is the lobster mushroom, which is a fruit body of a Russula or Lactarius mushroom that has been deformed by the parasitic fungus Hypomyces lactifluorum. This gives the affected mushroom an unusual shape and red color that resembles that of a boiled lobster.
Other mushrooms are not gilled, so the term "mushroom" is loosely used, and giving a full account of their classifications is difficult. Some have pores underneath (and are usually called ), others have spines, such as the hedgehog mushroom and other tooth fungi, and so on. "Mushroom" has been used for , , jelly fungi, coral fungi, bracket fungi, , and cup fungi. Thus, the term is more one of common application to macroscopic fungal fruiting bodies than one having precise taxonomic meaning. Approximately 14,000 species of mushrooms are described.
The stalk (also called the stipe, or stem) may be central and support the cap in the middle, or it may be off-center or lateral, as in species of Pleurotus and Panus. In other mushrooms, a stalk may be absent, as in the polypores that form shelf-like brackets. lack a stalk, but may have a supporting base. Other mushrooms including , Jelly fungus, earthstars, and Nidulariaceae usually do not have stalks, and a specialized mycological vocabulary exists to describe their parts.
The way the gills attach to the top of the stalk is an important feature of mushroom morphology. Mushrooms in the genera Agaricus, Amanita, Lepiota and Pluteus, among others, have free gills that do not extend to the top of the stalk. Others have decurrent gills that extend down the stalk, as in the genera Omphalotus and Pleurotus. There are a great number of variations between the extremes of free and decurrent, collectively called attached gills. Finer distinctions are often made to distinguish the types of attached gills: adnate gills, which adjoin squarely to the stalk; notched gills, which are notched where they join the top of the stalk; adnexed gills, which curve upward to meet the stalk, and so on. These distinctions between attached gills are sometimes difficult to interpret, since gill attachment may change as the mushroom matures, or with different environmental conditions.Stuntz et al., pp. 28–29.
In the basidiomycetes, usually four spores develop on the tips of thin projections called sterigmata, which extend from club-shaped cells called a basidia. The fertile portion of the Gasteromycetes, called a gleba, may become powdery as in the puffballs or slimy as in the . Interspersed among the asci are threadlike sterile cells called paraphyses. Similar structures called cystidia often occur within the hymenium of the Basidiomycota. Many types of cystidia exist, and assessing their presence, shape, and size is often used to verify the identification of a mushroom.
The most important microscopic feature for identification of mushrooms is the spores. Their color, shape, size, attachment, ornamentation, and reaction to chemical tests often can be the crux of an identification. A spore often has a protrusion at one end, called an apiculus, which is the point of attachment to the basidium, termed the apical germ pore, from which the hypha emerges when the spore germinates.
The cultivated mushroom, as well as the common field mushroom, initially form a minute fruiting body, referred to as the pin stage because of their small size. Slightly expanded, they are called buttons, once again because of the relative size and shape. Once such stages are formed, the mushroom can rapidly pull in water from its mycelium and expand, mainly by inflating preformed cells that took several days to form in the primordia.
Similarly, there are other mushrooms, like Parasola plicatilis (formerly Coprinus plicatlis), that grow rapidly overnight and may disappear by late afternoon on a hot day after rainfall. The primordia form at ground level in lawns in humid spaces under the thatch and after heavy rainfall or in conditions balloon to full size in a few hours, release spores, and then collapse.
Not all mushrooms expand overnight; some grow very slowly and add tissue to their fruiting bodies by growing from the edges of the colony or by inserting . For example, Pleurotus nebrodensis grows slowly, and because of this combined with human collection, it is now critically endangered.
Though mushroom fruiting bodies are short-lived, the underlying mycelium can itself be long-lived and massive. A colony of Armillaria solidipes (formerly known as Armillaria ostoyae) in Malheur National Forest in the United States is estimated to be 2,400 years old, possibly older, and spans an estimated . Most of the fungus is underground and in decaying wood or dying tree roots in the form of white mycelia combined with black shoelace-like rhizomorphs that bridge colonized separated woody substrates.
Most mushrooms sold in have been commercially grown on . The most common of these, Agaricus bisporus, is considered safe for most people to eat because it is grown in controlled, sterilized environments. Several varieties of A. bisporus are grown commercially, including whites, crimini, and portobello. Other cultivated species available at many grocers include Hericium erinaceus, shiitake, maitake (hen-of-the-woods), Pleurotus, and enoki. In recent years, increasing affluence in developing countries has led to a considerable growth in interest in mushroom cultivation, which is now seen as a potentially important economic activity for small farmers.
China is a major edible mushroom producer. The country produces about half of all cultivated mushrooms, and around of mushrooms are consumed per person per year by 1.4 billion people.Hall et al., p. 25. In 2014, Poland was the world's largest mushroom exporter, reporting an estimated annually.
Separating edible from poisonous species requires meticulous attention to detail; there is no single trait by which all toxic mushrooms can be identified, nor one by which all edible mushrooms can be identified. People who collect mushrooms for consumption are known as mycophagists, and the act of collecting them for such is known as mushroom hunting, or simply "mushrooming". Even edible mushrooms may produce allergic reactions in susceptible individuals, from a mild response to severe anaphylactic shock.Hall et al., pp. 22–24.Ammirati et al., pp. 81–83. Even the cultivated A. bisporus contains small amounts of , the most abundant of which is agaritine (a mycotoxin and carcinogen). However, the hydrazines are destroyed by moderate heat when cooking.
A number of species of mushrooms are poisonous; although some resemble certain edible species, consuming them could be fatal. Eating mushrooms gathered in the wild is risky and should only be undertaken by individuals knowledgeable in mushroom identification. Common best practice is for wild mushroom pickers to focus on collecting a small number of visually distinctive, edible mushroom species that cannot be easily confused with poisonous varieties. Common mushroom hunting advice is that if a mushroom cannot be positively identified, it should be considered poisonous and not eaten.
Psilocybin mushrooms, also referred to as psychedelic mushrooms, possess Psychedelic drug. Commonly known as "magic mushrooms" or shrooms", they are openly available in in many parts of the world, or on the black market in those countries which have outlawed their sale. Psilocybin mushrooms have been reported to facilitate profound and life-changing insights often described as mystical experiences. Recent scientific work has supported these claims, as well as the long-lasting effects of such induced spiritual experiences.
Psilocybin, a naturally occurring chemical in certain psychedelic mushrooms such as Psilocybe cubensis, is being studied for its ability to help people suffering from psychological disorders, such as obsessive–compulsive disorder. Minute amounts have been reported to stop Cluster headache and migraine headaches. A double-blind study, done by Johns Hopkins Hospital, showed psychedelic mushrooms could provide people an experience with substantial personal meaning and spiritual significance. In the study, one third of the subjects reported ingestion of psychedelic mushrooms was the single most spiritually significant event of their lives. Over two-thirds reported it among their five most meaningful and spiritually significant events. On the other hand, one-third of the subjects reported extreme anxiety. However the anxiety went away after a short period of time. Psilocybin mushrooms have also shown to be successful in treating addiction, specifically with alcohol and cigarettes.
A few species in the genus Amanita, most recognizably A. muscaria, but also A. pantherina, among others, contain the psychoactive compound muscimol. The muscimol-containing chemotaxonomic group of Amanitas contains no or , and as such are not hepatoxic, though if not properly cured will be non-lethally neurotoxic due to the presence of ibotenic acid. The Amanita intoxication is similar to in that it includes CNS depressant and sedative-hypnotic effects, but also Dissociative and Deliriant in high doses.
A third type of hallucinogenic mushroom is hallucinogenic bolete mushrooms such as Lanmaoa asiatica, which are said to cause people to experience Lilliputian hallucinations. These mushrooms have unknown constituents and an unknown mechanism of action, but appear to be distinct in their properties and effects from other hallucinogenic mushrooms and are currently being researched.
Some fungi, types of loosely called mushrooms, have been used as fire starters (known as tinder fungi).
Mushrooms and other fungi play a role in the development of new biological remediation techniques (e.g., using to spur plant growth) and filtration technologies (e.g. using fungi to lower bacterial levels in contaminated water).
There is an ongoing research in the field of genetic engineering aimed towards creation of the enhanced qualities of mushrooms for such domains as nutritional value enhancement, as well as medical use.
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