How to Identify Mushrooms and Truffles
Identifying fungi can be done using visual and aromatic cues, and chemical tests. A 10x hand lens or magnifying glass is an important tool to have for mushroom and truffle identification. The more serious mycophile will need a microscope to observe spore and tissue characters.
Here is a link to a diagram of general features of mushrooms: Mushroom Diagram
This should be useful as a reference when reading the material below.
The material under the following headings provides critical information to the identification of mushrooms:
Substrate Identifying the substance that a mushroom or truffle is growing on is important for diagnosing and discriminating species. This is because different fungi are specialized in obtaining their nutrition in different ways. Pathogenic and various ‘rot’ species grow from living trees, and can be quite host specific. If possible, identify the host plant. Saprotrophic fungi grow within, and fruit out of non-living substrates such as dead wood, humus, compost, dung, or ashes. In contrast, ectomycorrhizal fungi obtain their carbon nutrition from living trees in an intricately evolved mutualism. These fungi fruit out of the forest floor and amongst the root system of its host. Some ectomycorrhizal fungi show host preferences and even host-specificity. To help in their identification, be sure to look up and all around (not just down) and make note of the plant community when harvesting mushrooms and truffles.
There are many distinctive shapes or forms of mushrooms. Gilled mushrooms (agarics) differ from boletes and polypores by the shape of their fertile spore-producing layer, the hymenium. Morels, with their pitted hymenium are quite distinctive from coral fungi that have a smooth hymenium. For stipitate fungi (those having stems), the attachment of the cap and stem may be ‘central’, ‘lateral’ or ‘reduced’. Some mushrooms, such as the giant puffball (Calvatia gigantea) have no stipe. Fungi of the truffles form produce their spores on the inside of there fruiting body, and often fruit below the soil or at the soil surface.
Mushroom cap shapes*:
Spore color and shape
It is possible to get spore prints from a wide range of fungi including agarics, boletes, morels, coral fungi, and resupinate fungi. Often times, fungi have ‘spore-printed’ themselves, and you will see spores dusting the caps, along the stem or at the base of the mushroom. To obtain a spore print place a section of spore producing tissue on a piece of paper, cover to keep the humidity high, and place in a cool dark environment. Note the spore color after a few hours. Spores can range in color from white, buff, pink, tan, chocolate brown, rusty brown to black. With a compound microscope spore, diagnostic features including spore shape, size and ornamentation can be observed.
For further information on making a spore print see the following links:
The presence or absence of veils
A veil is a thin tissue the covers the spore-producing hymenium before the mushroom reaches maturity. Veils are common in some groups of mushrooms and boletes. They are most evident in young fruiting bodies. Many produce fragile or cobwebby veils that quickly disappear or weather away. Superficial wisps of tissue around the apex of the stem or the margin of the cap may be all the remains of a partial veil. Other times veils form a collar around the mushroom stem and are strikingly evident. In other cases, such as in deadly toxic species of Amanita, fruiting bodies are form in a sac-like structure, known as a volva, which is evident at the mushrooms base.
Types of mushroom veils*:
Hymenium (the fertile tissue)
Gills, gill attachment to the stem, gill edges and pores are evident on the underside of mushroom caps. A small mirror can place under a mushroom in the field to observe this character without disturbing the fungus. If the fungus has gills, their attachment to the mushroom stem can be ‘decurrent’, ‘adnate’, ‘adnexed’, ‘sinuate’or ‘free.’ See:http://www.tanelorn.us/data/mycology/myc_id_gills.htm and for drawings that demonstrate gill attachment.
The gill margin (distant edge) may be smooth or saw-toothed, and the color may be distinct. The gill spacing and thickness also varies between groups of fungi. Some have forking and cross-venation in their gills. In pored fungi, the shape and size of the pores varies.
Spacing of gills*:
The shape of the stem/stipe can also be a morphological characteristic used for identifying mushrooms. The following are some types of stem morphologies used in mushroom identification:
Texture and color change
Mushroom and truffle tissues vary in texture and can change color when handled. For instance, tissues of some boletes bruise blue when handled, due to oxidation reactions. Such reactions can be a diagnostic feature. When the cap or stem of mushrooms is damaged, it may stain red, yellow, green, blue or purple, or may not stain at all. Tissues may ‘peel’, ‘break’, may feel ‘slimy’ or ‘spongy’ or may be ‘woody’ or ‘fibrous’. The peridium, or outer surface of truffles, vary in texture and can range in color, texture (from smooth to warty), thickness and cellular arrangement.
The odor of fungi can be an important character for identifying some types of mushrooms and truffles. While subjective and variable between individuals, some fungi have distinctive odors that may range from ‘fruity’, ‘nutty’, ‘mushroomy’ to ‘phenolic’ or ‘putrid’.
Season, geography, weather
Mushroom species are adapted to certain places and conditions. Making note of the location (GPS coordinates are standard), time of year, and recent weather conditions and (day and night) temperatures can be helpful in identifying fungi, as are digital photographs of fresh specimen, paying special attention to the characters outlined above. Reputable taxonomic keys and field guides of the region of collection should be referenced for identifying fungi.
Follow this link for to a glossary of common terms:
*These diagrams are modified from Lincoff, G. H. 1981 National Audubon Society Field Guide to North American Mushrooms. Alfred A. Knopf, New York. ISBN 0-394-51992-2, as listed with the University of Saskatchewan.
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