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What is a mushroom?
Mushrooms are the fruiting bodies of certain fungi—the equivalent of the apple, not of the tree. Fungi, including those which produce mushrooms, are not plants; they are related to molds, mildews, rusts, smuts, and yeasts, and are classified in the Fungi Kingdom.
The fungal organism which produces the mushrooms you encounter on your lawn or in the forest is called a mycelium. It is composed of hyphae, which are "chains" of fungal cells (singular: hypha).
The mycelium itself is typically hidden in a substrate—within dead wood, for example, or in the soil. There, hidden, it secretes enzymes to digest organic matter, and the hyphal cells absorb nutrients through their cell walls. Depending on the species and the circumstances, the mycelium may be quite small, contained for example within the hull of a single black walnut; or it may be remarkably huge—some cover many acres of forest floor.
If a mycelium thrives, eventually it will have enough energy to reproduce. When conditions are "just so"—a combination of day length, heat, humidity, and other factors—the mycelium will generate new hyphae which, within several weeks, will develop into the highly organized structure we call a mushroom. (Note that not all fungi produce mushrooms; some reproduce at a microscopic level, usually asexually.) Mushrooms are specifically designed to support the production and dissemination of spores, which are the fungal equivalent of seeds.*
Spores are microscopically tiny—2,500 typical mushroom spores lined up end-to-end would only form a line one inch long.
Most mushrooms grow and decay rather quickly, but the organism remains and often will continue to produce more mushrooms for years, decades, or even centuries! Picking a mushroom is not the equivalent of uprooting an apple tree, but rather the equivalent of picking an apple, for the mushroom is not the organism—the hidden mycelium is!
Mushrooms evolved to enable fungi to produce spores in incredible quantities, typically by increasing the surface area of the spore-producing surface. The result is an exponential increase in the number of spores a given fungus can produce. It is easy to see how the formation of gills, for example, increases the mushroom's total surface area (see photo, right). The stalk helps raise the spore factory high, so a minute spore can hop a ride aboard the slightest breeze. The spores' high density and static electricity generally don't allow them to get very far, but every inch counts.
The slang term "toadstool" is best avoided, as it is ambiguous: to some people, "toadstool" implies a poisonous mushroom; to others, it means a mushroom with an umbrella-like shape.
An umbrella-shaped gilled mushroom is what most people think of as a "mushroom"—but many different forms have evolved that look quite different! Some mushrooms look like balls; marine coral; cups or saucers; shelflike growths on trees, logs or stumps; sponges; phalluses; clusters of icicles; tiny bird's nests (complete with eggs!); even cauliflower. Invariably, their designs help ensure successful reproduction.
Many mushrooms have also evolved various structural accessories. In some species, a universal veil encloses the entire mushroom at first (see photo, right); it helps by absorbing and trapping moisture, as does a partial veil—a separate tissue that extends from the upper stalk to the edge of the cap, covering the gills of some mushrooms until they're ready to produce spores.
Here is the best definition of the term "mushroom" as applied by mycologists (those who study fungi), mycophiles (those who love fungi), mycophagists (those who eat fungi), and consumer books on mushrooms and other fungi:
Note that some define the word "mushroom" differently, for example excluding morels and other ascomycetes. Furthermore, the term 'mushroom' is also often used to name the organism itself (the mycelium).
Yes, but that's just the tip of the fungal ecology iceberg!
Many fungi decompose dead organic matter such as leaves, wood, feces, etc. Many fungi are uniquely adapted to decomposing lignin—the hard "skeletal" tissue of wood. No other organisms can do this with any efficiency whatsoever, so forests as we know them simply could not exist without mushrooms and other fungi to break down the dead wood and return the nutrients to the soil. But other fungi play other vital ecological roles, and few people even realize it!
For example, many species of fungi are mycorrhizal (the term translates to "fungus-root"); rather than merely decomposing organic matter for a living, they have a vital symbiotic relationship with trees and other green plants. At least 90% of all land plants, including all trees, have mycorrhizal fungi! The plant "feeds" the fungus some of the carbohydrates it makes through photosynthesis; the fungus dramatically increases the tree's roots' absorption of water and certain essential minerals, such as phosphorus and magnesium, which the plants have poor access to without their fungal partner's help.
Without mycorrhizal fungi, most plants—including the grass on your lawn—would not survive and thrive! (That's why "chemical lawn services" will not apply fungicides to eliminate mushrooms for homeowners who don't like "toadstools" on their lawns—the chemicals would also kill the essential beneficial fungi.)
Not all mycorrhizal fungi produce mushrooms as part of their reproductive strategies, but many basidiomycete fungi do. Because of the way the fungal cells are physically arranged in relation to the root cells of the host tree or plant, mycorrhizal basidiomycete fungi are more specifically referred to as ectomycorrhizal, meaning that the cells of these mushroom-producing fungi do not penetrate the cells of the plants' roots. Ectomycorrhizal fungi are primarily found living in this vital symbiosis with certain kinds of trees. In North America, these include especially certain trees in four major tree families: Pine (including pine, hemlock, fir, spruce and larch [tamarack]); Beech (including beech, oak and chestnut); Birch; and Willow (including willow, aspen, poplar and cottonwood). Other kinds of mycorrhizal fungi that don't produce mushrooms (most notably the endomycorrhizae) are more typically associated with other kinds of trees and plants.
Therefore, certain forest types are especially interesting places for studying mushrooms. My favorite "mushroom woods" in upstate New York are mostly places where there is a mix of oak, beech, Eastern hemlock and birch trees. Other interesting forest types in the northeastern states include pine barrens (which feature a mix of oaks and pines), pine and spruce forests (including reforested areas), and tamarack (larch) bogs. In contrast, maple, black cherry and hickory trees' mycorrhizal fungi don't produce mushrooms, so forests populated mostly with those kinds of trees are generally a lot less interesting places for mushroom study.
Other fungi, including some mushrooms, have a different role: they infect and kill things—insects, trees, even people (particularly those with weakened immune systems)—for a living. Fungi cause most diseases of insects, as well as many diseases of trees and other plants… not to mention such common maladies as toenail fungus, yeast infections, and "ringworm."
As previously stated, fungi are principally responsible for breaking down dead wood (especially lignin), and the fungi that have evolved the advanced capabilities necessary for decaying dead wood are mostly species that produce mushrooms. Partly because of this evolutionary advancement, and partly because of their highly evolved sexual reproductive strategies, mushroom-producing fungi are often referred to as "the higher fungi."
Some fungi have evolved to take advantage of multiple food sources. For example, the Oyster Mushrooms you can buy fresh at many grocery stores break down and digest cellulose (that's the chief soft component of wood), but they have also developed mechanisms for literally trapping and then eating tiny little "worms" called nematodes; this gives them access to extra nitrogen.
Mushrooms generally have specific habitat needs. For example, the highly popular edible/medicinal mushroom known as Maitake, Hen of the Woods, or the Sheepshead mushroom (Grifola frondosa, see photo, right), is by far the commonest at the base of large oak trees. Other mushrooms are very specific, for example, several mushrooms are only found growing under Eastern white pine trees.
They seem to grow overnight!
Yes—they seem to. In truth, they don't grow as fast as they "seem" to.
The Easy Stuff
Instead of seeds, fungi produce spores. In the case of fungi which produce mushrooms, that's the sole purpose of the mushroom—it is a spore-producing structure. (Some fungi produce spores differently, without producing a visible structure that could be called a mushroom.)
The "body" of the fungus is called the mycelium. It is a tangled network of microscopically-thin filaments called hyphae, and it is typically hidden—in the humus on the forest floor, within decomposing wood, wrapped around the rootlets of a green plant, or wherever else serves as its dining room.
When conditions are right (humidity, day length, temperature, etc.) a fungus will produce new hyphae that are far more organized than those in the mycelium: a mushroom. This process takes longer than most people think—typically several weeks or more from the time the mushroom first starts forming until the time it is able to produce spores.
The More Technical Stuff
Most mushrooms are Basidiomycetes, all of which reproduce sexually (though some have methods of asexual reproduction as well). Specialized cells called basidia (singular: basidium) produce the spores, which are more specifically called basidiospores, on tiny projections called sterigmata (singular: sterigma). (Some mushrooms—most notably the morels and related "cup mushrooms"—are Ascomycetes; they produce spores differently, within tube-like cells called asci [singular: ascus through a distinctly different sexual reproductive mechanism].)
If two basidiospores of the same species are lucky enough to germinate into primary or monokaryotic mycelia (each cell of which has one nucleus—see "A" and "B" in the illustration) in close proximity to each other, they can "mate" by forming a secondary mycelium with two nuclei per cell. This secondary or dikaryotic mycelium (see "C" in the illustration) is potentially capable of eventually producing more mushrooms.
It is in the basidium that meiosis and karyogamy occur… in short, two nuclei become four—one for each of the four spores each basidium produces. (There are some exceptions to this, e.g. mushrooms whose basidia typically produce only two spores each and basidiospores that contain two nuclei).
Do all mushrooms grow in the dark?
No. Many mushrooms require light for proper development. Little-known fact: several kinds of mushrooms GLOW in the dark!
How many kinds (species) of mushrooms are there?
It is estimated that there are at least 10,000 species in North America alone. NOTE: In mycology, we use the term "variety" to refer to a variant (often differentiated by different coloration) within a species; the term species implies a biological species, i.e. a group of organisms that can sexually reproduce with one another. Hence, statements such as "he has seen dozens of varieties of mushrooms in his woodlot" is troublesome… it should read "he has seen dozens of species of mushrooms in his woodlot."
About 250 North American species are known to be edible (though only about half of these are truly worthwhile), and a similar number are known to be poisonous; the rest we're not sure about. NOTE: Most of the common, conspicuous, attractive mushrooms are known to be either edible or toxic.
Many species are very difficult to identify correctly, often requiring microscopic study and scientific books (and there are still plenty of species that haven't even been named yet!). Often, identifying a specimen to genus is as good as one can expect.
None of the "rules of thumb" work—for example, contrary to various folk myths, all mushrooms that grow on wood are not safe edibles; a silver spoon or silver coin will not tarnish if cooked with any poisonous species; and some mushrooms whose caps can be peeled are not safe to eat.
There is only ONE way to know whether a mushroom you've found is edible: You must identify the mushroom; only then can you find out what human experience with it has been! The stalk must be examined very carefully—is there a ring of tissue (technically called an annulus) on the upper stalk (see photo, right)? Is there a cup-like sac (a volva) around the very base of the stalk? (The latter is a feature of the often-fatal Death Cap (Amanita phalloides) and Destroying Angel (A. virosa) mushrooms.)
How to Make a Spore Print
With most mushrooms, a very important character to consider is the spore print color. Though spores are microscopic, mushrooms produce millions of them. Cut the stalk off a mushroom and place the cap right-side-up on a sheet of clear, stiff plastic, then cover it with a bowl and leave it overnight. It will usually deposit millions of spores, and you can see their color en masse. White paper can be used, but clear, stiff plastic is much better for viewing a pale spore print. The clear trays that are used by many delis for products such as salads work well, as do clear, stiff report covers.
How dangerous is it to drive a car? If you're drunk or careless, it is VERY dangerous; if you're sensible and pay attention, it is reasonably safe. Most mushroom hunters have never gotten sick from eating wild mushrooms. It is a good principle for the novice to stick to the most easily identified edibles, such as morels, puffballs, and half a dozen others.
Newspaper reports of serious mushroom poisonings often refer to the victims as "experienced mushroom hunters." But, as a rule, they don't even know what a spore print is; they just think they know what a certain edible mushroom looks like. Most victims of life-threatening mushroom poisoning in North America are people from Southeast Asia; they mistake the Death Cap mushroom (Amanita phalloides) for the edible "Paddy-Straw" (Volvariella volvacea) mushroom. The two are similar in several ways—cap color, size, and the white "cup" around the base of the stalk—but different in others (for example, the Paddy-Straw has a pink spore print, the Death Cap a white spore print; and the Death Cap has a partial veil while the Paddy-Straw mushroom lacks one). The Paddy Straw mushroom occurs in tropical and subtropical areas worldwide; the Death Cap, does not occur in Southeast Asia, so folks from that part of the world are unaware of the lethal "look-alike" that lingers in some American parks and forests.
Can a person become poisoned by touching or handling toxic species?
No. The only way for a poisonous mushroom to harm a human is for him to consume at least part of it.
Amateur mycologists soon learn that using "common" names for mushrooms is a tricky business, as each field guide seems to have its own set of "common" names. To minimize confusion, amateur mycologists rely on the scientific names of mushrooms. At first, this may seem intimidating, but in reality the scientific names are no more difficult than some we all know: Tyrannosaurus, Rhinoceros, Hippopotamus.
While many mycologists, mycophiles and others will confess that they have had positive—even life-changing—experiences with hallucinogenic mushrooms, many will also confess that they have had negative experiences with hallucinogenic mushrooms. Here is a word to the wise: Take it slow!
The illegality of Psilocybe and other genera with hallucinogenic properties is not the only issue here. Contrary to popular perception (at least in some circles), "bad trips" featuring paranoia and depression rather than enlightenment and euphoria are as much a danger with Psilocybe and other psychoactive mushrooms as they are with LSD. A good percentage of mushroom poisoning cases involve victims who thought they were going to have good "recreational" or "spiritual" experiences but ended up either having "bad trips" or eating something dangerously toxic.
If you are committed to finding and eating wild hallucinogenic mushrooms, prepare to learn a lot about field mycology first—or risk paying a terrible price for making a serious mistake!
An Important Note About Amanita muscaria
Apparently, because this common mushroom contains neither psilocybin nor psilocin, its possession, sale and use is not illegal in most states. Because this species has a reputation for being psychoactive, there are numerous Websites on the Internet from which one can purchase dried A. muscaria. I urge the curious to resist the temptation, as you'll be paying an absurd fee for an experience you will not likely enjoy.
First, Kombucha is not a mushroom.
One area of mycology regarding which I have little knowledge or interest is mushroom cultivation. No one knows mushroom cultivation better than Paul Stamets of Fungi Perfecti.
The study of mushrooms and other fungi is a fascinating area for amateur naturalists. There are three ways to learn more, and combining the three is the best way to learn:
There are many mushroom field guides available for North America; the following are some of the most popular ones along with a select listing of books about other aspects of mushrooms such as cultivation.
Classes and Conferences
Classes in mushroom identification, taught by qualified experts, are a great way to learn more. Contact your local college's biology department to see what they have to offer. You might also try nature centers; botanical gardens; cooperative extension offices; museums; and other educational organizations.
David Fischer is available to teach mushroom identification courses, workshops, and seminars. He especially enjoys presentations to the general public, especially the remarkable slide-illustrated lecture Please Don't Call Them Toadstools. See his schedule of upcoming events or contact him at the e-mail address shown below.
Some mycological organizations sponsor annual conferences (called 'forays') complete with field trips, workshops and lectures. Two in particular are recommended:
The North American Mycological Association (NAMA) has numerous membership benefits, including publications and multimedia programs.
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