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Forest Mushrooms: Part I – Mushroom Basics
This article is the first of a series in the S&W Report on forest mushrooms. Topics covered in the series include mushroom anatomy, life cycle, habitat and key identification features of some of Ontario’s common forest mushrooms.
In Part I, we will look at “mushroom basics” – anatomy, life cycle and key features used in identifying mushrooms, including some myths about edible mushrooms.
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Warning! Edible mushrooms are often very similar in appearance to poisonous kinds. The information provided in this article should not be used alone in the identification of mushrooms intended for consumption
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Mushroom Basics
The term mushroom is more of a common expression given to the fruiting body of certain fungi, rather than having a precise taxonomic meaning. Fungi belong to their own kingdom and are separate from the plant and animal kingdoms.
Mushrooms only represent a small fraction of the estimated 1.5+ million fungi species. In Ontario, there are about 5,000 species of fungi and there are over 10,000 species found across North American. Of this number, approximately 250 species are known to be edible, most belong to groups generally referred to as mushroom or cup fungi.
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The Destroying Angel is a member of the genus Amanita, a group of mushrooms that are extremely poisonous. Look for the three key identification features: (1) the ring around the stem near the cap, (2) the cup at the enlarged base of the mushroom and (3) the white gills under the cap. 1
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Fungi are unique, unlike plants, fungi cannot make their own food. Many mushrooms are saprophytes that live off dead organic material, by breaking this material down and absorbing the nutrients. A second group of mushrooms obtain their food by forming a mutually beneficial relationship with another living organism (symbionts). While a third group are considered a parasite or pathogen because they infect and live off a living organism, often killing the host organism.
Mushroom Anatomy
The anatomical features of mushrooms are used to characterize and identify mushrooms. However, it is important to note that many species develop only a few of these features and some groups have different anatomy. For example, the boletes have pores versus gills to house spores, and bracket fungi lack a stem. Figure 1 provides an illustration of a typical mature mushroom and its anatomical features.
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Figure 1. Anatomy and life cycle of a typical mushroom, showing many anatomical features that are used to characterize and identify mushrooms. Many species develop only a few of these features and some groups have different anatomy. 2
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The following is a description of the basic anatomical features of a mushroom:
Cap — the cap (or pileus) is the top part of the mushroom.
Scales — the scales are the remnants of the veil and appear as rough patches on the surface of the cap.
Gills or Pores — the reproductive structure of mushrooms takes the form of gills (or lamellae), pores, or in some cases, as teeth or spines. They form on the underside of the cap and house the spores.
Ring — the present or absence of a ring (or annulus) is an important feature used when identifying mushrooms. The ring is remnant tissue of the veil that encircles (shirt-like) the stalk of a mature mushroom. The veil is the tissue that connects to the stem to the cap during the early stages of the development of the fruiting body. Not all mushrooms have a ring.
Stem — the stem (or stipe) is the main support structure of many mushrooms; however, not all mushrooms have a stem. The stem may be attached to the cap in the centre, off-centre or at the side.
Cup — the basal cup (or volva) is a remnant of the veil and forms a cup-shaped structure at the base of the mushroom. Not all mushrooms have a cup.
Important note: mushrooms with both a cup and a ring generally belong to the genus Amanita, a group of mushrooms that are extremely poisonous.
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Commonly called the Jack-o'-lantern, (Omphalotus illudens) this poisonous species is fairly easy to identify. It grows in clusters on wood, its colours are bright orange, its gills run down the stem, has orange-yellow gills, is poisonous. 4
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Mushroom Life Cycle
Mushroom fungi basically have two parts to their life cycle. There is a vegetative stage where the mycelium form, collect water and nutrients needed for growth and a reproductive stage dedicated to spore reproduction.
The mushrooms we find on the forest floor are actually the reproductive structures (fruiting bodies) produced by some fungi. As part of their life cycle, a mature mushroom will discharge millions of microscopic spores that form in the gills or pores under the cap. These spores are easily dispersed by the wind, landing on a suitable site (e.g., rotting wood, forest litter, etc.) where they germinate and form a network of tiny thread-like cells (mycelium). Under the right environmental conditions, the mycelium grows and the sexual reproduction stage is initiated (i.e., a mushroom is produced). Refer to Figure 1.
Unlike the mushroom, which die off and disappear quickly, the mycelium will live off their hosts for many years, producing fruit (mushrooms) on an annual basis. Picking a mushroom is comparable to picking an apple from a tree. The tree, or in this case the mycelium, is left behind to produce new fruit next year.
How to Identify Mushrooms
With thousands of fungi species growing in Ontario, the identification of mushrooms isn't easy. It requires an understanding of their basic anatomical features such as the cap, stem, gills, odour and taste (see below). Other macroscopic features that should be examined include its form of growth (e.g., clusters, single stem), habitat, and the time of year it appears.
For accurate identification it is recommended that identification should be done when the mushroom is mature, when all its physical features have fully developed.
Cap — examine the diameter of both the button and mature caps. Note the texture of the cap's surface (e.g., smooth, furry, scaly, etc.), its shape (e.g., conical, flat, bell-shaped, convex, hemispherical, etc.) and its colour.
Stem — examine the length and diameter of the stalk. Look at its shape. Is it bulbous, tapered, club shaped or equal in diameter from the apex to its base? Note its colour, and the colour and texture of its contents (internal tissue). Examine whether a ring or basal cup is present. Note: not all mushrooms have stems.
Gills — determine whether gills or pores are present. Identify how the gills are attached to the stem (e.g., decurrent, free, notched, ascending, sinuate, etc.) and look at their spacing, depth and colour.
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This photo of the Milky Cap (Lactarius vinaceorufescens) mushroom shows gills that are broadly attached and well spaced. 3
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Odour and taste — various species of fresh mushrooms can have a distinctive taste and odour. Note: if you use taste to identify mushrooms, taste and spit. Do not swallow any tissue; some mushrooms are poisonous!
Spore print — a key identification feature in identifying mushrooms is their spore print. Different mushroom species produce different coloured spores. Although individual spores are not visible to the naked eye, an accumulation of them can leave behind a distinctive coloured spore print. Sometimes you may be lucky and find a coloured dusting (spore print) on the leaves or the ground under mushroom or on the tops of the mushrooms when they are found growing in clusters and the caps overlap.
Unfortunately, finding spore prints in the field is not always possible and you will want to make a print at home in a more controlled environment. This involves removing the cap from a mature mushroom and placing the cap, hymenium facing down, on a small sheet of glass. The cap and glass sheet is then placed inside a covered container. It is left outside at ambient temperatures for 12 to 24 hours. After 24 hours, remove the sample and place the glass sheet over a white or black sheet of paper and note the colour of the spore print produced.
The best way to begin learning how to identify mushrooms is to purchase several field guides, or better still, take a course and learn from a local expert. If you are considering harvesting mushrooms to eat you should also learn how to identify some of the common poisonous mushrooms. Note: this article should not be used alone in an attempt to identify mushrooms intended for consumption.
Mushroom Myths
There are many false myths about mushrooms. Here are a few examples:
- Poisonous mushrooms tarnish a silver spoon.
- If it peels, you can eat it.
- All mushrooms growing on wood are edible.
- Mushrooms that squirrels or other animals eat are safe for humans.
- All mushrooms in meadows and pastures are safe to eat.
- All white mushrooms are safe.
- Mushrooms can be detoxified by parboiling, drying or pickling.
- Is it true that if you put a penny in the skillet with poisonous mushrooms, the penny will turn green.
- Poisonous mushrooms must taste bad.
- Mushrooms are edible if they turn black when they are boiled with garlic.
- Mushroom can poison someone just by holding it or smelling it.
References
Biology, Ecology, and Social Aspects of Wild Edible Mushrooms in the Forests of the Pacific Northwest: A Preface to Managing Commercial Harvest, General Technical Report PNW-GTR-309. USDA Forest Service.
Mushrooms of Algonquin Provincial Park, The Friends of Algonquin Park. 2006
Edible forest mushrooms and other fungi (Non-Timber Forest Products in Ontario: An Overview),
Forest Research Information Paper No. 145, Ontario Forest Research Institute, Ontario Ministry of Natural Resources.
Recommended Reading
Medicinal Mushrooms: An Exploration of Tradition, Healing & Culture, by Christopher Hobbs. Available on Amazon.com
North American Mushrooms: A Field Guide to Edible and Inedible Fungi, by Dr. Orson Miller Jr. Available at the Forest Shop (613) 233-4283 for $35.95.
Mushrooms of Ontario and Eastern Canada, by George Barron. Available at the Forest Shop (613) 233-4283 for $29.95.
In the Next Edition
In Part II of this series, we will look at some of the more common wild edible mushrooms found in Ontario. This article will provide the reader with information on the habitat and key identification features for a dozen different species.
Photo credits and Acknowledgements
1 Joseph O'Brien, USDA Forest Service, Bugwood.org
2 USDA Forestry Service
3 Joseph LaForest, University of Georgia, Bugwood.org
4 Robert L. Anderson, USDA Forest Service, Bugwood.org
This article appeared in the Summer/Fall 2007 (Volume 48) edition of the S&W Report, the newsletter of the Ontario Woodlot Association.
© 2008 Ontario Woodlot Association
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