From morels to chanterelles, toadstools to truffles, fungi have been a source of fascination since the earliest hunter-gatherers first foraged for them. Today there are few, if any, places on Earth where fungi have not found themselves a home—their habitats span the poles and the tropics, mountaintops and backyards.
Packed with facts and photos, this book introduces you to fungus in many forms—some parasitic, some poisonous, some hallucinogenic and some with healing properties that can be tapped for pharmaceutical products. Then of course, there are the delicious mushrooms that are prized by epicureans and gourmands worldwide.
Each species here is reproduced at its actual size, in full color, and accompanied by a scientific explanation of its distribution, habitat, association, abundance, growth form, spore color, and edibility. With information on the characteristics, locations, distinguishing features, and occasionally bizarre habits of these fungi, you’ll find in this book the common and the conspicuous, the unfamiliar and the odd—including a fungal predator, for instance, that hunts its prey with lassos, and several that set traps, including one that entices sows by releasing the pheromones of a wild boar.
“How dazzling is the world of mushrooms? The fan-shaped cinnabar oysterling looks like something you would find undersea. The violet webcap is vibrant. These are among the more than 600 fungi described and illustrated in this scholarly and beautiful book.”—TheNew York Times
“Anyone with an appreciation of the beauty of nature will enjoy.”—Grand Forks Herald
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About the Author
Peter Roberts was for fourteen years a senior mycologist at the Royal Botanic Gardens, Kew. He has undertaken field trips throughout the British Isles and Europe, as well as North, Central, and South America, the Caribbean, and Africa, and has published extensively on temperate and tropical fungi. He is the coauthor of New Naturalist: Fungi and is on the editorial boards of the journals Field Mycology, Mycological Progress, Czech Mycology, and Persoonia. Shelley Evans was conservation officer for the British Mycological Society for ten years and is on the executive committee of the European Council for the Conservation of Fungi and the IUCN world specialist group for fungi. She is coauthor of Pocket Nature: Fungi and is on the editorial board of the journal Field Mycology. She is an experienced field mycologist, having undertaken field trips throughout the British Isles and Europe, as well as North America.
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The Book of Fungi
A Life-Size Guide To Six Hundred
By Peter Roberts, Shelley Evans
The University of Chicago PressCopyright © 2011 The Ivy Press Limited
All rights reserved.
WHAT ARE FUNGI?
A hundred years or more ago, fungi were thought of as lower plants or cryptogams, on a par with mosses and liverworts. They did not produce flowers and their seeds were very small, but they were still plants of a sort. However, it gradually became clear that fungi had little or nothing to do with plants. They were not made of cellulose, like plants, but of chitin (a substance more usually associated with insects). They did not contain chlorophyll and could not use sunlight to convert carbon dioxide into sugars. As a result, in the 1960s, they were placed in their own grouping—the kingdom Fungi. Curiously, modern DNA research puts the fungi even further from plants. Fungi are part of the opisthokonts—a group that also includes the animals. It seems animals and fungi once had a common ancestor, some time after plants went their separate way.
HOW DO THEY WORK?
While animals and plants are made up of cells, fungi are made up of microscopically thin, tubelike hyphae. When they clump together, these hyphae can often be seen as cobwebby threads in damp leaf litter, in compost, or even on the surface of moldy food.
Fungi "eat" by absorbing food through their hyphal walls, mostly in the form of simple sugars and amino acids. If these are not immediately available, they can extract them from more complex substances by secreting enzymes. Animals, including ourselves, use similar enzymes in the stomach to digest food. Fungi do the same—only their digestive system is external.
FINDING YOUR WAY ROUND A MUSHROOM
When we look at a fungus, we are generally looking at a sporocarp—the spore-producing fruitbody that may be called a mushroom, a toadstool, a puffball, and so on. The real fungus—the cobwebby mycelium made up of hyphae—is generally beneath the soil, or spreading through the leaf litter, or running through a fallen log. It is rather as if oak trees grew hidden underground and all we saw were acorns periodically forming on the surface.
Take the Death Cap (Amanita phalloides, see here) as a classic example of a fungal fruitbody. It takes several weeks to develop on the mycelium, but once developed it expands quite rapidly from the button stage to maturity. It is this expansion that gave rise to the old idea of mushrooms and toadstools "growing" overnight.
The fruitbody has a distinct stem that lifts the cap and gills off the soil surface, the better to release spores into the air. The spores themselves (the fungal equivalent of seeds) are microscopic and are formed in their millions on the gills, which are covered by the cap. In the Death Cap, the immature gills are protected by a veil (membrane) that ruptures as the cap expands, leaving a ring on the stem. A second, universal veil encloses the whole fruitbody when young, the remains of which are left as detachable patches on the cap and as a sack-like volva at the stem base.
Other fruitbodies—of bracket fungi, stinkhorns, or morels—vary enormously in shape and in their methods of spore liberation, but the basic spore-bearing principle is the same.CHAPTER 2
PLANT & ANIMAL PARTNERS
Over 90 percent of the world's plant species depend on fungi for their nutrition. The two have evolved side by side and the partnership continues to this day, fungi and plants together supporting our whole global ecosystem. Other new fungal partnerships have also evolved—not only with plants, but with bacteria, algae, insects, and other animals.
HOW PLANTS GET THEIR NUTRITION
Fungi are excellent recyclers, producing enzymes that break down complex materials to release their nutrients. They were among the first colonists of dry land and interacted with early, primitive plants. The relationship may have been parasitic at first, but gradually evolved into a symbiotic one. Fungi obtain sugars from their plant partners, and plants take essential nutrients from fungi, principally nitrogen and phosphorus.
The exchange occurs through mycorrhiza ("fungus roots"). In the commonest form, endomycorrhizal fungi live inside a plant's root system. These fungi belong to the phylum Glomeromycota—an unfamiliar group to the majority of fungus enthusiasts, as most can only be seen under a microscope. Far more familiar are ectomycorrhizal associations. Ecto means "external," and in this association the fungi live outside the plants, forming an interface with them by wrapping their hyphae around the roots. Comparatively few plant species are involved, but these include some of our commonest trees—oak, beech, birch, willow, alder, pine, fir, spruce, hemlock, eucalyptus, and southern beech. Their fungal partners include many woodland agarics, boletes, chanterelles, and truffles.
LICHENS—TWO SPECIES IN ONE
Fungi cannot photosynthesize, but lichenized fungi have found a way round this by entering into an intimate partnership with algae or cyanobacteria (photosynthesizing bacteria). The fungi depend absolutely on their partners and never occur without them, but the algae and cyanobacteria can exist on their own—so the relationship is a bit one-sided. The algae and cyanobacteria do gain a safe home, however, and an opportunity to spread into areas they could never colonize on their own. The partnership is an extremely successful one, since lichens are extremophiles—able to grow in some of the world's most inhospitable environments.
FUNGUS GARDENS FOR TERMITES AND ANTS
Fungus–animal partnerships have also evolved, one of the most specialized being the termite fungi of Africa and Asia. Everyone knows that termites eat wood, but they have problems digesting it. Some species have microscopic fungi in their gut that break down cellulose, but others keep fungi in their nests that perform the same service. This partnership is so ancient that a whole genus of fungi called Termitomyces has evolved. The termites propagate and "garden" the fungus mycelium by bringing in fresh plant material and keeping everything at the right temperature and humidity. In Central and South America, similar fungus gardens are tended by leaf-cutting ants.
AMBROSIA BEETLES AND DUTCH ELM DISEASE
Bark beetles often carry fungal spores with them, sometimes in special pouches called mycangia. When burrowing into bark, the spores are released and the fungi—all of them wood-rotting species—grow in the beetle tunnels. The beetles or their larvae then graze the mycelium. This helps both fungi and beetles, but not always the trees. In the British Isles, Scolytus beetles spreading the exotic fungus Ophiostoma novo-ulmi have led to the epidemic called Dutch Elm Disease which has killed off an estimated 20 million elm trees.CHAPTER 3
One of the reasons why fungi have developed a bad name for themselves—especially in the English-speaking world—is their popular association with rot and decay. Yet without decay, our whole terrestrial ecosystem would swiftly grind to a halt. It is fungi that are the great recyclers, turning dead plant matter—fallen leaves and stems, branches and trunks—into nutrient-rich humus and soil.
TURNING DEAD PLANTS INTO SOIL
Most fungi are saprotrophs—a term that means "eaters of dead matter." To rot things down and release the sugars and amino acids upon which they feed, fungi have evolved an array of useful enzymes. Some of these enzymes break down cellulose—the basic substance out of which plants are made.
The rotting process starts while leaves are still attached to the plant. Many microfungi colonize leaves, lying dormant until the leaf is ready to fall. The fungi then proliferate and start the breakdown process ahead of any competitors. When the leaf falls, there are other fungi ready and waiting. In some tropical rainforests, the leaf may not even reach the ground, since aerial webs of fungal rhizomorphs (threadlike structures) can catch a falling leaf and trap it. The aptly named Horsehair Fungus (Marasmius crinisequi) is one little agaric that can perform this leaf-catching trick.
WOOD-ROTTING—A JOB FOR SPECIALISTS
All plants contain cellulose, but woody plants also contain lignin—the substance that makes wood hard. Brown rot fungi break down the cellulose and leave the brown lignin as a cake of powder. More common are the white rot species that break down both cellulose and lignin, leaving nothing much more than grayish white, stringy remains.
As with leaves, the wood-rotters get to work early. Many of them are present as small, dormant propagules in living wood, patiently waiting for their particular branch or twig to die. A change in the chemistry signals the end, and the dormant fungi get to work while the dead or dying branch is still on the tree. Most of these fungi are highly specialized, often growing on particular kinds of tree and no other.
When the branch hits the ground, however, the wood-rotting generalists battle over its remains—a struggle in which chemical weapons may be deployed to attack and defend a rich resource. Some species are quick colonizers, but they are replaced by slower, but more pugnacious, species, so that a succession of different fungi appears on a fallen branch, as it gradually rots away. A few highly developed specialists—mostly bracket fungi—can tackle heartwood. Found in the core of trunks and limbs, this is hard, dense, dead wood often full of tannins, oils, and other toxic chemicals. Eventually (and it may take decades), the heartwood is rotted away and the tree becomes hollow, yet still perfectly healthy—a wildlife haven in its own right.
HORNS, HOOVES, AND HAIR
Some fungi release enzymes that break down keratin, the main component of hair and feathers, hooves, horns, and skin. Most of these keratin-rotters are microscopic and some—like Ringworm—can cause problems if they infect living skin, nails, or hair. The Horn Stalkball (Onygena equina) is one of the larger species, producing fruitbodies like small puffballs on old shed horns and other animal remains. Its relative, O. corvina, grows on old, discarded feathers.CHAPTER 4
PESTS & PARASITES
There is sometimes a fine line between a mutually beneficial relationship and a parasitic one—but a few fungi certainly cross that line and are undeniable parasites on plants, on animals, and even on other fungi. The same is true for pests. A fungus that rots down fallen trees in forests may be a useful species. But if it does the same thing to timber in the home, it is a pest.
HONEY FUNGUS—THE GARDENER'S BANE
The Honey Fungus (Armillaria mellea) is a wood-rotting species that has evolved a particularly efficient means of colonizing new resources, producing tough rhizomorphs (which resemble old-fashioned, black bootlaces) that can spread underground. When there is plenty of dead wood around, it is harmless. But when there is not, it will attack living trees and shrubs. In a garden, the Honey Fungus can run riot—and little can be done to stop it.
Household timber is generally too dry for fungi. But if the moisture content rises above 20 percent, some species can get to work. Dry Rot (Serpula lacrymans) is one that tolerates drier conditions than most. The waffle-like fruitbodies can also produce spores in such vast quantities that they can be a health problem in themselves. If the moisture content rises above 40 percent, then Wet Rot (Coniophora puteana) and other species can join in the destruction.
Creosote and other wood preservatives were invented to protect external timber from rotting, but a few fungi are creosote-tolerant. The Train Wrecker (an alternative name for Neolentinus lepideus) had a bad reputation for rotting old-fashioned, wooden railroad sleepers. Other fungi used to be pests of wooden telegraph poles or pit props in mines.
Cordyceps species attack a wide range of insects, from butterflies to beetles, wasps, and even ants. One of the best-known is the Chinese Caterpillar Fungus (Ophiocordyceps sinensis) which infects moth larvae. When the caterpillar goes underground to pupate, the fungus grows in the insect, eventually producing its own fruitbody above the ground. Traditional Chinese medicine regards this oddity—called "winter worm, summer grass"—as highly desirable, so that now collecting fruitbodies (with mummified caterpillar attached) is a profitable business.
FUNGI THAT HUNT WITH LASSOOS
It may seem improbable, but a few fungi are active predators, albeit on a microscopic scale. They mostly set traps for miniscule nematodes (eelworms). The species involved include the familiar Oyster Mushroom (Pleurotus ostreatus), which has sticky projections on its hyphae. Passing nematodes find themselves glued to the projections. The fungus assimilates the nematodes and uses them as a source of nitrogen. Some small cup fungi (Drechslerella species) have evolved lassoo-like traps—rings of hyphae that can swiftly constrict when triggered by a nematode passing through them.
FUNGI THAT PARASITIZE EACH OTHER
It should be no surprise to discover that some fungi parasitize their fellow fungi, often in rather peculiar ways. Among the oddest are agarics in the genus Squamanita. These species—all of them uncommon—parasitize the fruitbodies of other agarics, typically producing their own cap and gills on top of the host's stem.
The Lobster Fungus (Hypomyces lactifluorum) is another strange-looking object. It is a fungus that engulfs agarics, keeping their shape but coating them in a crust of its own miniature fruitbodies. Even stranger is the fact that these parasitized fruitbodies are considered edible and good.CHAPTER 5
FOOD, FOLKLORE & MEDICINE
Human beings are omnivores, and fungi have undoubtedly formed part of our diet since we first evolved. Cultural peculiarities, however, have led to some nations and communities being mycophiles—lovers of fungi—while others are mycophobic, with a deep distrust of the whole poisonous kingdom. Not surprisingly, this often colors folk beliefs and associations. The use of fungi in traditional medicine follows a similar pattern, but modern scientific medicine has been keen to explore their potential, with the result that many of today's most successful pharmaceuticals are fungus-derived.
ONE AND A HALF MILLION TONS OF MUSHROOMS
Around one and a half million tons of Cultivated Mushrooms (Agaricus bisporus) are produced worldwide each year. Their cultivation can be traced back to seventeenth-century France, where a substantial industry gradually developed based in cavernous, disused mines around Paris. Even today Cultivated Mushrooms in France are known as champignons de Paris. Modern commercial production was developed in the United States and mechanized in the Netherlands.
Perhaps surprisingly, Agaricus bisporus only accounts for some 40 percent of world cultivation. Other species, including the Shiitake (Lentinula edodes), the Oyster Mushroom (Pleurotus ostreatus), and the Wood Ear (Auricularia cornea), together make up the rest, with production and consumption predominantly in eastern Asia, though many of these species are becoming more popular in the west.
THE CALL OF THE WILD
Many edible fungi are still collected in the wild, not just by mushroom enthusiasts but on a commercial scale. The reason is that ectomycorrhizal species—those that form an intimate association with trees—cannot be cultivated away from their hosts. The Cep or Porcini (Boletus edulis) and the Chanterelle (Cantharellus cibarius) are among the most sought-after species, but in Japan a fascination with the Matsutake (Tricholoma matsutake)—often presented as expensive gifts—has led to a huge and lucrative import trade.
TRUFFLES—THE ULTIMATE PRIZE
Truffles (Tuber species) are underground fruitbodies of ectomycorrhizal fungi whose spores are spread by animals attracted by pheromones and other tempting aromas. Some of these tempt humans as well, and species such as Tuber magnatum have long been rare and costly items for European gourmets. In recent years, truffles have been semi-cultivated with varying success in truffières—plantations of trees inoculated with mycelium—but they still remain one of the ultimate luxury foods.
MAGIC MUSHROOMS AND WITCHES' BUTTER
In mycophilic countries, fungi often played a positive role in folk tales, some hallucinogenic species—such as the Fly Agaric (Amanita muscaria)—achieving an almost sacred status among shamans seeking contact with the spirit world. In mycophobic countries, they were regarded with suspicion. The Witches' Butter (Exidia glandulosa) was one of several fungi whose mysterious appearance could only be explained by witchcraft, while circles of the Fairy Ring Champignon (Marasmius oreades) marked the dangerous enclaves of the Little People.
THE FUNGAL PHARMACY
Fungi have long played a part in traditional medicine—especially in eastern Asia, where species such as the Lacquered Bracket (Ganoderma lucidum) are still highly valued today. In modern western medicine, antibiotics such as penicillin (derived from the mold Penicillium chrysogenum), cholesterol-lowering statins (derived from species such as Aspergillus terreus), and immunosuppressive cyclosporins (derived from Tolypocladium inflatum) are among many clinically proven pharmaceuticals with a fungal origin.
Excerpted from The Book of Fungi by Peter Roberts, Shelley Evans. Copyright © 2011 The Ivy Press Limited. Excerpted by permission of The University of Chicago Press.
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