Study Of Mushrooms

Press, Volume CVI, Issue 31085, 14 June 1966, Page 20

Study Of Mushrooms

At a conservative estimate, there are more than 1000 species of mushrooms and toadstools in New Zealand. Many are edible; some are deadly poisonous; and many have economic significance through their effects on the growth of trees and other plants. In spite of this, only about a quarter of the species occurring in this country have been scientifically described and classified. The task of completing the classification has been undertaken by Dr R. F. R. McNabb, of the plant diseases division, of the Department of Scientific and Industrial Research.

With the co-operation of biological observers of the Forest Service, he is collecting specimens of the various species from all over New Zealand, and in his laboratory in Auckland is recording their characteristics and preserving specimens for storage in the herbarium. The results of his work will be of value to other scientists, because a complete classification will facilitate rapid identification of any mushroom or toadstool which appears to be causing damage, or to be pathogenic, or beneficial to plant life.

The classification will also be useful to foresters. Some of these fungi are parasitic, as, for example, the honey fugus Armillariella mellea which attacks the roots of ; trees.

i Others play a part in breaking down litter to form humus. Others again form associations with trees which are beneficial to the growth of the trees. Aid Tree Growth

In some cases, trees will not grow well without their associated fungus, and lit is a common practice, when planting new forests, to introduce soil from under existing trees of the same species along with the seedlings in order to ensure that the appropriate fungus is present. Better knowledge of just which fungi are concerned will enable foresters to establish or preserve these associations with more certainty.

Quite apart from these aspects, Dr McNabb’s work should have considerable interest for the layman, since it has already indicated that there are unexploited possibilities in many New Zealand mushrooms and toadstools from the gastronomic point of view.

Dr. McNabb tastes as he goes—not for the purpose of finding nice things to eat, but because taste provides an additional character in class!-

fication. Nevertheless, he has discovered that many species, other than those commonly eaten, have pleasant and delicate flavours. New Zealanders in general eat only three species of these fungi—the common field mushroom, Agaricus campestris; the cultivated mushroom, Agaricus bisporus; and to a much lesser extent the horse mushroom, Agaricus arvensis. Continental people who have come to live in New Zealand have widened the range slightly. Recognising some of their own European species here they have begun to use them, specially some of the Boletus species from under pines. Dr. McNabb believes the range could be further extended, not only by exploiting neglected species already growing here, but also by introducing useful edible species from overseas. The Boletus family includes some of the most highly esteemed of the edible fungi. In particular, there is Boletus edulis, which is a favourite in Europe and America but does not occur in New Zealand. This species is generally associated with oaks and similar broad-leaved trees, but there is a variety of it which occurs under pines and is beneficial to their growth. Dr. McNabb considers that for this reason, as well as for its gastronomic value, it would be a worthwhile introduction to New Zealand. Eaten in Europe

Another species he thinks might well be introduced for the same two reasons is Lactarius delidosus. This species, not a bolete, is commonly eaten in Europe and Britain. It is quite distinctive in colouring, and could not be confused with other species growing under pines in New Zealand. There could possibly also be room for introduction of some cultivated species. The New Zealand mushroomgrowing industry is based almost wholly on Agaricus bisporus, but there are some other species that are successfully cultivated overseas. For example, the Japanese use a toadstool that grows on cut oak logs, and in other Asian countries a species that grows on rice straw is used. Among the edible species already growing in New Zealand, but seldom eaten by New Zealanders, are the common puffball and the fairy ring fungus. When young and still firm, the puffballs can be sliced, fried in butter, and used in various dishes or in salads. The fairy ring fungus, Marasmius oreades, can be readily dried, threaded on string, and kept as a flavouring for use when there are no fresh mushrooms available.

Dr. McNabb warns, however, that one must be able to recognise edible species before it is safe to eat mushrooms or toadstools. There is no truth, he says, in the old

wives* tale* that if a species is poisonous it will blacken a silver spoon, or that poisonous species will not peel readily. “One can’t be too careful in selecting which fungi to eat, because we now have in New Zealand two of the most poisonous fungi known,” he says. “These species are Amanita phalloides (the death cap) which was recently positively identified in Auckland, and Amanita muscaria. “Both have crowded white gills which do not change colour. Both have a ring on the stem near its top, and a swollen base to the stem. Amanita phalloides has a yellowish olive or greenish cap with white patches, and usually grows around introduced trees such as oaks. Amanita muscaria has a bright red cap with white patches, and is found almost exclusively in pine woods.” Clearly, there are dangers in sampling unfamiliar fungi, and Dr. McNabb, in his own tasting programme, carefully avoids genera, such as the Amanitas, which are known to include poisonous species. For the layman who wishes to experiment with mushrooms and toadstools, he suggests first a reading of some of the handbooks on European fungi which are available in New Zealand, and which at least make it possible to recognise which are edible among the introduced species growing in this country.