Mushrooms & Other Fungi

by: Twila Robar
September 1981

IMAGE:  Mushrooms & Other Fungi Diagram

For centuries fungi, or more specifically mushrooms, have been objects of mystery. They have become a traditional part of fairy tales and an important part of ancient magic rite. Fleshy mushrooms are served as delicacies in famous restaurants and the microscopic mould fungi such as the Penicillium sp. form the basis of the most important anti-biotic drugs. Without fungi we would be buried in organic debris, we could not eat our daily bread, nor enjoy our wines and cheeses. Yet with the exception of those parts of the world where mushrooms have been used as a foodstuff for centuries, they have often been regarded with revulsion and fear. even today the fungi are misunderstood, and the persistence of myth and suspicion encourages even more confusion.

The family of Fungi is very large, widespread, and diverse, and no one volume could contain all the species of fungi known to us. This article discusses the biology and lifestyles of some of the more common mushrooms and other fungi found in our fields and woodlands.

The term "mushroom" is confusing as well. In one sense it refers to the cultivated or canned variety of mushroom, or to the field mushroom ( Agaricus campestris ), which we enjoy picking on balmy fall mornings. The term also encompasses all those fungi which form a typical mushroom. "Toadstool" traditionally refers to any poisonous mushroom; however, since both poisonous and edible species occur in closely related groups, the term is of little practical use.

To add to the general confusion, not all fungi form mushrooms. The majority of the fungus family is made up of mould fungi which remain microscopic throughout their lives. thousands of these fungi can be isolated from soil, dung, plant and animal remains, and from streams, rivers and the edge of the sea. though we may not notice them directly, the activities of microscopic fungi influence our lives in many ways. They remove waste materials and maintain the fertility of the soil. Man has used their chemical processes to manufacture numerous useful materials ranging from wine and cheeses to therapeutic drugs. They can also affect our health and destroy our crops.

Mushrooms have a way of appearing rather suddenly, as if by magic, a property which may explain some of the suspicion and mystery that surrounds them. To understand the way fungi live, it is necessary to understand a few basic principles.

All living things are made up of cells, and fungal cells, rather than in brick-like units, are in long strings or filaments known as hyphae. Mushrooms are made up of thousands or millions of root-like hyphae. As a hypha grows it produces enzymes which digest the complicated organic substances that surround it, and break them down to simple molecules. The hyphae then absorb the molecules to provide energy for future growth.

Hyphae grow for miles, tunnelling their way through soil, tree stumps or logs, and then, if the conditions and season are right, they aggregate to form small knob-like beads, the beginning of the mushroom body. The mushroom expands, usually rapidly, and emerged through the ground, often overnight.

The principal parts of a mushroom are illustrated by the diagram above representing a section through an Amanita. The fruiting body consist of a stem-like stipe which supports and expanded umbrella-like cap called the pileus. On the underside of the cap are the gills or lamellae on which the spore-producing structures are located.

Each spore, given a suitable habitat, is capable of producing a hypha to form a new colony. However, the survival rate is so low that fungi must produce enormous quantities of spores to compensate for this. Most spores are dispersed by air currents, and the smaller they are, the farther they will go. The common field mushroom has been calculated to produce 1,800 million spores at an average rate of 40 million per hour. In some species the spores mature and are dispersed in a relatively short space of time, whereas others may produce spores for several months.

In some mushrooms the young plant is completely enclosed in a sheath of tissue, the universal veil or volva. As the mushroom grows the veil is broken and the mushroom emerges, often leaving remnants around the base or on the cap. The universal veil and volva are not present in all mushrooms, but are important characteristics in identifying the dangerous family of Amanita mushrooms.

Biologically the mushroom can be likened to an apple on a tree and the underground hyphae can be compared to the tree's branches. Hyphae in the soil act as a colony. An interwoven mass of hyphae is known as a mycelium, which is the spawn stage that grows and colonizes new ground, providing the energy for the fruiting stage. Mycelial masses are often seen when old trees, stumps, or woodpiles are torn apart.

The majority of fungi live on the remains of dead animals and plants or on other organic waste. without their digestive activities, the organic litter would accumulate until the forest became a huge pile of dead leaves and trees. Some fungi are not particular where they grow. Others require special conditions and are consequently restricted to one or a few specific habitats. For example, the Shiny Ganoderma ( Ganoderma tsugae ) is always found on hemlock stumps or logs.

A second group of fungi grows on organisms while they are still alive and cause serious damage to trees and other plants. Some of the plant-infectors, like the bracket fungi, are easily seen because of their large fruiting bodies. The Birch Polypore ( Piptoporus beteulinus ) commonly infects birch trees. Its mycelium grows into the heartwood and eventually kills the tree. The fungus continues to grow on the dead tree, often bearing fruiting bodies long after the tree is dead. A number of gilled mushrooms are parasites. The Honey Mushroom ( Armillaria medllea ) causes serious damage to a wide range of coniferous and deciduous trees.

The third major group of fungi is again associated with certain trees, but rather than harming the trees, they are often beneficial forming an intimate relationship with the tree's root system. Fungi which form such a relationship with higher plants are known as mycorrhiza and are of considerable importance in the growth of many trees. A number are very species-specific; for example ( Suillus grevellei ) Grevell's Boletus, is invariably found under larch.

Mycorrhizal fungi stimulate tree growth, especially on poor soils deficient in minerals. The hyphae increase the tree roots' absorption area. Careful investigation suggests that rather than obtaining essential carbohydrates from dead plant materials, mycorrhizal fungi take up sugars directly from the host tree.

Fungi as a group reproduce by the production of spores. These are essentially the seeds of the fungus. Although single spores are microscopic, they form conspicuous masses. A spore print can be made by placing a mature, spore-bearing mushroom cap on a sheet of white paper. The cap is then covered with a bowl and left for a few hours at room temperature. A print of the spores will be left on the paper. Spores vary in colour from white to yellow, pink, purple brown or black. Spore colour is a very stable characteristic of mushrooms and is useful for identification purposes.

Mushroom Hunting

The richest selection of mushrooms and toadstools is to be found in the woodlands, particularly in the autumn. Different forest types contain their own distinctive fungi.

In conifer woodlands the higher fungi are represented by the following, to name a few: the yellow Tricholoma, commonly known as the Horseman ( Tricholoma flavovirens ), the red-gilled Cortinarius (Cortinarius semisanguineus), and the spiny undersurfaced Hydnum (Hydnum imbricatum). Mature conifer woodlands have a limited understory because the tree density is high and the shortage of light restricts the growth of plants beneath the trees. Mycorrhizal fungi are often necessary for the trees to develop their full potential.

The beautiful colours of the deciduous woodlands in autumn are an additional bonus for the mushroom hunter. The mushroom flora in this habitat is remarkable in its diversity and richness. Here can be found some of the finest edible varieties as well as some of the most deadly. Look for the Horn-of-Plenty (Craterellus fallax), and the rusty capped Leccinum (Leccinum aurantiacum).

Mushrooms of the mixed woods may be found in all types of woodland provided that climate, especially rainfall, temperature and soil conditions are right. Some common mushrooms of the mixed forest are the salmon to brownish Laccaria ( Laccaria laccata ), the Sickener ( Russula emetica ), the yellow-orange capped Fly Agaric ( Amanita muscaria ), and the popular Chanterelle ( Cantharellus cibarius ).

To most people the quality of mushrooms that first arouses interest is whether it is poisonous or not. Unfortunately there are no clear-cut tests or rules to determine this. Just as the collector can identify a raspberry or a blueberry from unknown berries, he can learn to identify several common mushrooms. The Meadow Mushroom ( Agaricus campestris ), the Chanterelle ( Cantharellus cibarius ), and the Shaggy Mane (Coprinus comatus) are edible varieties and can be easily identified with practice. Unrecognized species should be avoided and never picked for food.

The Destroying Angel ( Amanita virosa ) is fairly common - and deadly poisonous. Nova Scotia is excellent Amanita country.

Whether they are large or small, delicious or deadly, beautiful or bizarre, mushrooms and other fungi are fascinating. Perhaps this brief encounter with them will be an inspiration for a walk in the forest and a closer look at some of Mother Nature's finest work.