Decomposers in life's recycle

Which organisms produce delicious food or deadly poison, cause disease yet yield some of the most useful of all medicines, can stink like a rotting corpse or produce a delectable aroma that makes them a luxury food item, and are loathed and feared by some people and worshipped by others? The answer of course is fungi or mushrooms, the topic of this fascinating book by a real mushroom enthusiast. The author is a microbiologist whose research deals with bacteria, but his consuming hobby is mushrooms. The combination of his enthusiasm for mushrooms and his scientific accuracy has produced a volume that covers the widest possible range of topics about mushrooms.

The use of numerous species of edible fungi and the way in which they can be cooked into a wide range of tasty dishes is interwoven throughout the book. One senses that this is the greatest attraction of fungi for the author.

However, the many aspects that are covered show clearly that mushrooms are very much more than a source of food or poison. Wisely the text is interspersed with clear warnings that in order to eat a strange mushroom one must be absolutely sure of the identification to determine whether it is edible or poisonous. There are no simple rules and it is a fallacy that all poisonous mushrooms turn silver spoons black, stain yellow or do not peel. This book is not a field guide for the identification of fungi but rather a compendium of well-researched and interesting information about them. Once identification is certain from a field guide to mushrooms it would be well worth trying out some of the culinary suggestions of the author.

Mushrooms have shaped the course of history. Agrippina, the wife of Roman emperor Tiberius Claudius, used a mushroom to poison her spouse. The Russian cavalry was defeated by the Turks in the battle of Astrakhan in 1722 because many of the soldiers died or got sick from eating bread contaminated with ergot, a fungus that infects rye and other cereals.

Fungi belong to a kingdom of their own, the Mycota, that is neither plant nor animal. This includes the familiar mushrooms that are the spore-producing, fruiting body that is only part of the whole organism. Moulds, yeasts, smuts and mildews are all part of the fungal kingdom.

Unlike green plants, fungi do not produce their own food through the process of photosynthesis and are therefore parasites or saprophytes that live on other organic material. As a result, they cause many diseases of plants and animals such as Dutch elm disease, potato blight or athletes foot, but they also play a vital role as recyclers of organic material.

If it were not for these great decomposers that recycle so much organic matter, the world would become buried under an ever accumulating mass of dead leaves, branches and other natural litter.

Life on earth as we know it today would not exist without the fungi, and they are ubiquitous. The author calculates that there are at least ten trillion kilograms of fungi on earth. That is two tons of fungi for every human. It is, therefore, hardly surprising that fungi are so varied, so interesting and cannot be overlooked.

We read here about giant puffballs weighing over 22 kilograms and measuring a metre in diameter which can produce 20 trillion spores, of hallucinogenic mushrooms, fairy rings on lawns, and that mushroom sex consists of thousands rather than just two genders. Truffles with their irresistible odour are the most delectable of fungal foods, sold for as much as $1,000 per pound, but even the evil-smelling, phallus-like, stinkhorn can be eaten if cleaned of the slime on the cap.

Although many of the edible species described are mainly from the author's experience in North America, many of the mushrooms are equally familiar to a European reader because of the widespread distribution of so many species.

The fungal anecdotes, legends and history given are derived from the worldwide literature and travels of the author. A large number of well-known British authorities on fungi are quoted such as E. J. H. Corner, P. H. Gregory, David Hawksworth and John Ramsbottom.

The book conveys both the importance of and the fascination of fungi. It is extraordinary that only 69,000 of the estimated 1.6 million species of fungi have been named and classified. It is to be hoped that the author has conveyed more than a general interest about a vital group of organisms, and that some readers will be encouraged to become professionally interested in a much neglected area of biological science.

In the words of the author: "Going on a mushroom walk fulfils all sorts of other yeamings beside the gratification of foraging for natural food. I am excited by the zest of the hunt, challenged by the demands of identification, pleased by the encounter with species that have a special meaning to me, and charmed by especially handsome specimens."

Perhaps the town of Kiryu in Japan has got its priorities right. It has a mushroom park, a research institute, museum, shrine and hotel all devoted to mushrooms. Mushrooms are weird and wonderful organisms that merit much more attention than they are given.

Sir Ghillean Prance is director, Royal Botanic Gardens, Kew. He has studied the use of edible mushrooms by the Indians of northwestern Amazonia.