The Mycota, or the Fungi, are usually conisidered to be a separate taxonomic Kingdom from either plants or animals. True Fungi are eucaryotes with chitin lined cell walls, that live by digesting food substances. They are not directly photosynthetic. Cells tend to be syncytial, the cells run-together into long tube-like multi-nucleate 'hyphae'. This continous cytoplasm is most pronounced in the lower fungi. In the ascomycetes and basidiomycetes, there are partial septa dividing up the hyphal cytoplasm into segments. Most fungi are isogametic, meaning that the gamete mating-types are very similar in size and shape. Fungi often live in soil, but some are parasites on other organisms, including plants. Fungi have many physiological and genetic similarities to animals. The chytrid moulds even produce flagellated gametes, like animal spermatozoa.

Spore Type	Forms	Toadstool Characteristics
Ascospores:		Sexual ascospores on the upperside of the ‘toadstool’. Spore-bearing surface is a matrix of many apothecia or perithecia.
Basidiospores:		Sexual basidiospore layer often on the underside of the toadstool cap or bracket. The spore bearing surface usually originates inside the sporocarp. A tissue-cover breaks to expose the spore-bearing surface. This surface often has either a pore, maze or a gill-like structure.

Most fungi qualify as multi-cellular organisms. They even have different cell types. Though, the differences between these cell types are rather subtle. The morphogenesis of the fungi is not homologous with animals, and is not even closely analogous. A fungus is vaguely analogous to a plant in some ways. Like a plant, a multi-cellular fungus is a modular organism composed of reiterated units. Most hyphal types are not ‘fated’. Given the appropriate stimulus, a hyphal tip is capable of reverting to some other role. That is, somewhat like plants the ‘somatic’ versus ‘germ-line’ distinction is not too applicable to the fungi. Meiotic cells are not as flexible as most other cell types, once they have been set on course. Otherwise, almost any fragment ripped out of a fungus can act as a ‘stem cell’ and clone itself into a whole new individual.

Probably, the fungi derived their multi-cellular condition independently of either plants or animals. In other words, the common ancestor of all three ‘higher’ kingdoms was probably a single-celled protozoon. Genetic comparisons suggest that fungi and animals parted ways roughly one thousand-million years ago in the Early Proterozoic.

Fungi are heterotrophic organisms that generally live inside, on the outer layers of, their food media. The true fungi feed by osmotrophy. They lack true phagocytosis. They feed by excreting enzymes, and then reabsorbing the digestible products of these exoenzymes. This mode of life is not unique to fungi. In fact parallel strategies exist in many protozoa and even in the bacteria. In fact many bacteria form ‘mycelia’ somewhat as fungi do. This is why many bacteria were once called ‘bacterial moulds’ and given names such as: ‘ray fungi’ (Actinomycetes), ‘fission fungi’ (Schizomycetes) and mycoplasmas.

Reference

Moore, David. 2005. Principles of Mushroom Developmental Biology. International Journal of Medicinal Mushrooms. 7: 79-101.

Some toadstool-forming fungi cause wood decay. But many of the fungi which cause plant diseases are microfungi, with tiny sporocarps. Some, such as the endophytic fungi exist mostly as mycelium, and do not often form fruiting bodies.

Morels have long been considered to be both saprobic and mycorrhizal. However, in the 1990s it was suggested that morels are sometimes parasitic. Morels are certainly saprobes, at least some of the time. This is why it is possible to cultivate morels in vitro, with difficulty. Morels can also be mycorrhizal, they seem to benefit many species of trees and herbs. The morel's mycelium forms mantles around rootlets. Root cells are penetrated with little hyphae (haustoria) and feed off the host plant’s nutrients. Normally this relationship is endo-mycorrhizal. The morel exchanges mineral nutrients, as if by way of trade, for the plant's carbohydrates. The morel's association with roots is not always mycorrhizal. Apparently when roots die, or they are dying, the morel's haustoria harvest the sugars inside the root cells. In this manner morels wait poised to become root-rotting agents, as soon as their role as mycorrhizal fungi is over. Probably the fruiting bodies are an final attempt to reproduce before its food supply runs out. This is the probable explanation for why morel mushrooms seem to be most common under dying trees. It is even possible that morels may switch to a parasitic role as their host tree weakens. Whether or not morels are ever true parasites is still an open question.

Morels are not a major cause of root decay. They rot only the most peripheral roots of trees. And it is mostly soluble carbohydrates, not cellulose, that the morels consume. Therefore, morels are not a significant factor in the destruction of root support. Morels are very unlikely to instigate tree falls. Since morels are edible, their growth is often encouraged by landowners. Morels are not considered a pest, rather they are a gift from the earth.

Honey Mushrooms

Honey mushrooms or stumpers, in the genus Armillaria , are another group of edible fungi. They are members of the Tricholomataceae family. These mushrooms tend to become large and floppy, and nearly translucent as they mature. These fungi also have mycelia that can glow in the dark, under certain conditions. Stumpers are distinct enough in appearance, but there are deadly poisonous toadstools that superficially look like them. Therefore, one should become familiar with the genus before harvesting them. These mushrooms can be slightly toxic if under-cooked, especially if they are consumed along with alcohol.

Stumpers are important as agents of wood rot. Some species are considered to be pathogens. Not every species is a pathogen to living trees. It is commonly supposed that the Armillaria mellea is a highly variable species with many subspecies in it. It is now suspected that this species is the most active pathogen in the genus.

Naturally, it was long assumed that the aggressive honey mushroom parasitises the hapless entoloma. Recent research strongly argues that it is the entoloma which parasitises the honey mushroom. What were once thought to be distorted entoloma, turned out to be mostly composed of the honey-mushroom’s tissue. Apparently, the ‘aborted’ mushrooms are deformed honey mushrooms riddled with feeding mycelia from the entoloma! Such deformed toadstools are called carpophoroids. Often malformed fungal masses are due to parasites of one kind or another (Czederpiltz et al 2001).

For more information visit Dr. Tom Volk's Fungi Page .

The genus Boletus is typified by toadstools with stout smooth stipes, rounded caps, and with pores under the cap. Most species are tan, brown, ochre, golden or reddish. The reddish species tend to be less flavorsome, sometimes they are even bitter, or even poisonous. Boletes are generally mycorrhizal. The exceptions tend to be parasites on other fungi. In the boreal forest one often finds boletes neatly tucked between the twigs of spruce trees. These boletes were not placed there by trolls! They were collected by squirrels. Many boletes apparently exploit rodents as agents of dispersal.

Boletes in general are similar to the polypore toadstools - but much more like agaric ‘mushrooms’ in shape. Once it was thought that boletes were closely related to the genus Suillus. The suillus toadstools are similar in appearance, but often have rough textured stipes and larger pores. It is now known that this similarity does not reflect genetic closeness. Boletes are genetically closer to some of the gilled-toadstools than to the suilli. Furthermore, recent research indicated that there many more bolete species than hitherto expected. Many of these species are extremely close look-alikes, differing in their mycorrhizal associations and other subtle details.

The bitter bolete (Tylopilus felleus) is not a true bolete. Unfortunately this terrible tasting toadstool is more common in Ontario's boreal forest than is the edible bolete. It is one of the few non-red bolete-like fungi that is not edible. It differs in appearance from the edible bolete mostly in subtle details of form.

Jack o’Lanterns

Jack o’ lantern mushrooms (Omphalotus olearius, formerly O. illudens) is a yellow to vivid orange toadstool that sometimes is found near root crowns. Commonly it grows in clusters on oak stumps or on the root-crowns of moribund hardwoods. Most often the fruiting bodies are visible in the late summer or autumn. The fungus is a pathogen, but it seems to be most common on trees which are already stressed.

Superficially the fully expanded jack o' lantern toadstool looks like a chanterelle. Unlike the chanterelle the jack o’ lantern toadstool does have distinct gills. The true chanterelles have ridge-like rills instead of distinctly formed gills. The jack o’ lantern toadstool is fairly poisonous. The toadstool sometimes glows brightly enough to be visible on dark nights. In French the fungus is known as the clitocybe lumineux because of its bioluminescence.

Psilocybes

Psilocybe toadstools are members of the Strophariaceae family. The word ‘psilocybe’ means roughly ‘bald-head’, as most psilocybes have smooth caps. These fungi are mostly saprobes. Some live in dung. Unlike the closely related Stropharia, there are very few edible psilocybes. In fact most psilocybes are actually hallucinogenic to humans. Liberty caps (P. semilanceata) are ‘little brown mushrooms’ that often grow in pastures. The large psilocybe (P. cubensis) is a paler version that looks more like a stropharia. It grows on cattle dung, and is one of the most famous ‘magic mushrooms’. Psilocybes vary in halluciongenic potency. The related Stropharia, mostly, are not hallucinogens.

Psilocybes are one of the few toadstools to become embroiled in mythology and pseudoscience. Because of their popularity as hallucinogens, there has been much exaggeration about the safety and danger of theses shrooms.

Amanitas

The Amanita toadstools are a genus of mycorrhizal fungi that grow under trees. They have tall straight stipes with ‘collars’ and often have remnants of the primordial veil stuck to their caps. Their gills are usually pale, unlike the true ‘agarics’. Very few amanitas are edible, in fact many are deadly poisonous. The white ‘destroying angel’ (A. virosa) is very deadly. A single such toadstool can permanently destroy a human’s liver. On the other hand, the handsome red-orange fly-agaric (A. muscaria) is not quite as poisonous, but a few have died from it. Fly-agaric does cause nausea, and it is also strongly hallucinogenic.

Myxomycetes

Sometimes one can find organisms that appear to be tiny toadstools or puffballs. These ‘toadstools’ are typically less than one centimetre tall. These tend to grow on moist deadwood, bark, leaf duff or mulch. Even weirder are the early phases in the life-cycle of these moulds that form gelatinous blobs. These blobs actually crawl about, slowly, before they condense into spore-bearing bodies. These strange creatures are examples of myxomycete slime moulds. The slime moulds are amoeboid protozoa in the Myxomycota taxon.

There are hundreds of species of myxomycetes. The Stemonitis spore-bodies look like tiny pipe-cleaner brushes. The Lycogala resemble little puffballs. Others like the Hemitrichia form fuffy clubs, almost looking like tiny toadstools. The Fuligo are different, their spore bodies are more like large blobs. Slime moulds feed on bacteria, spores and smaller protozoa. They tend not to be full-fledged saprobes.

Taxonomy & Biology

Fungi are typified by the fact that they can have two distinct kinds of spore types. They can have a sexual phase (the teleomorph), or they can disperse via an asexual phase (the anamorph). These spores can be quite different in form. Furthermore, many species of fungus produce one spore type much more often than the other. Since hyphae look so much alike, it has often been difficult to determine the connection between the asexual and sexual forms. Hence the fact that many fungi have been given two species names! Only with the advent of genetic analysis are many of the anamorphs and teleomorphs being matched up. Some fungi seldom, if ever, take on a teleomorphic phase, these fungi imperfecti reproduce asexually most of the time.

Spores produced on fruiting-bodies are usually haploid. In fact, a growing mass of fungal tissue (the mycelium) can be haploid. This haploid mycelium may clone itself with asexual spores. When two mycelial filaments (hyphae) of opposite mating types (sexes) meet they fuse. In the non-chytrid fungi this initial sexual fusion is incomplete. The union of the two hyphae produces a dikaryotic hypha, a tissue with two sets of nuclei. A dikaryotic mycelium may then grow from this union. The mycelium may grow for a long time-period without complete sexual fusion taking place. Actual sexual fusion of the nuclei occurs during the formation of a fruiting-body (sporocarp). In other words, a toadstool appears as the sexual fusion is in progress.

TAXONOMY of FUNGI in CONTEXT

Sporocarp Type	Forms	Sporocarp Characteristics
Sporangium (pl. Sporangia):		Sexual or asexual spores in sac-like ‘pin-head’ on a stock.
Conidium (Conidia):		Asexual spores exposed on hyphal stocks.
Chlamydospore:		Asexual spores formed by hyphal division & swelling.
Pycnidium (Pycnidia):		Flask-shaped organ containing asexual conidia.
Apothecium (Apothecia):		Cone or cup-shaped organ containing sexual spores.
Perithecium (Perithecia):		Flask-shaped organ containing sexual spores.

Toadstools are merely the fruiting bodies of the fungus. The greater mass of a fungus is mycelium. In fact, altogether some fungi are composed of tonnes of mycelial clones extending through hectares of soil. Technically, some fungal mats are the largest known organisms on Earth. Certainly a soil fungus can be larger than a baleen whale, a redwood tree, or a whole stand of poplar clones! Although, some would argue that masses of cloned mycelium don’t count as single individuals.

Toadstools:	Mushroooms, toadstools & macrofungi.
Mycorrhizae:	Plant root and fungus symbiosis.
Glomeromycota:	Endomycorrhizal pin-moulds: Some
Saprobic Fungi:	Soil fungi and edaphic ecosystems.
Myco-heterotrophic Plants:	Plants that exploit mycorrhizal fungi.
Lichen Symbiosis:	Fungi and algae which together form lichens.
Fungal Bioluminescence:	Fungi that glow in the dark.
Wood Decay Fungi:	Parasitic and saprobic fungi of plants.
Endophytic Fungi:	Benign fungal parasites in plant tissues.
Fungus Gardening Insects:	Fungi grown and harvested by insects.
Hypogeous Fungi:	Truffles and tuckahoes.
Toxic Toadstools:	Poisonous and hallucinogenic fungi.
Myxomycete Fungoids:	Fungus-like protozoan organisms.
Oomycete Fungoids:	The fungus-like 'water moulds'.

Saprobic organisms are a major part of the edaphic flora and fauna. It is saprobic organisms which generate the humus component in top soil. Because of saprobes, dead organisms are reduced to microscopic organic particles and emulsions. The broken down bio-matter forms the humus which lends the top soil its dark colour. This also allows the the organic matter to be re-useable by plants. One litre of top soil can contain literally millions of individual bacteria, fungi, oomycetes and sundry protozoa. Some of these creatures are free-living, others form biofilms on mineral particles in the soil. Fungi are the second most massive living component in soil after bacteria. Insects, and other animals, account for but a tiny fraction of the biomass in dirt.

Fungi play a crucial role in terrestrial ecosystems. Fungi have managed to occupy a greater number of niches on land than they do in the sea. Soil fungi live-off everything from dead bacteria, to dead animals, to dead wood. It has been estimated that fungi may comprise up to twenty percent (20%), or more, of the living biomass on land. Much of the remaining biomass consists of dead plant matter and bacteria.

The number of fungal species which have a niche in soil ecosystems is immense. Most of the moulds are zygomycete pin-moulds, members of the Phylum Archaemycota. The Rhizopus and Mucor species are common pin-moulds, which can occur in soils, or on rotten plant matter. Both of these pin-moulds can infect wounds in animals, under unusual conditions. Zygorrhynchus are common pin-moulds in humus. Some of the pin-moulds, such as Arthrobotrys, are both saprobic and predaceous. A nematode, once subdued, is then penetrated by the feeding hyphae of the mould. The niches in soil ecosystems are not always sharply defined. Some of the soil fungi are glomeromycetes, others are ascomycetes or basidiomycetes. Some are microfungi, others form large toadstools. The Endogone are common soil fungi, some of which are mycorrhizal. The endogone moulds are now known to be related to the aquatic chytridiomycetes. Some of the soil moulds, such as Saprolegnia, are oomycetes, and not really fungi.

Some of the soil fungi grow best on fresh dung. They do not proliferate well in soil lacking fresh organic matter. The well-studied Phycomyces grows on dung, and other relatively ‘fresh’ organic matter. The Phycomyces hypha can sense light, and grow towards it. In this way it can seek out an open space in which to release its spores. The ‘hat-thrower’ fungi in the genus Pilobolus have a rather interesting means of projecting their spores. When mature, the hat-thrower shoots its sporangium a great distance with the hydrostatic pressure of a sporangiophore ‘connon’. The spore masses may then stick to grass blades, where they could be swallowed by herbivores. The sprores can survive the digestive tracts of animals. These several dispersal mechanisms of dung fungi allow them to disperse to other dung piles, which may be rather far from one another.

Yeasts are unicellular fungi. Strangely, they are not usually members of the Archaemycota. Yeasts are generally ascomycetes, and some even form short hyphae, and many sprout little asci. Yeasts, such as the Saccharomyces, are usually saprobic in one way or another. They live much like protozoa in the organic matter of humus.

Quite a high proportion of the moulds are fungi imperfecti, or asexual fungi. Imperfect moulds are usually, but not always, ascomycetes. Fungi in the genus Alternaria are common soil fungi. If alternaria grows indoors it is called ‘black mildew’, and it can be strongly allergenic. The mildew-like Cladosporium fungi are are common in rich humus. Aspergillus and Penicillium moulds, with their bluish conidia, are a common in both humus and in freshly rotting plant matter. Some of these moulds appear to live in both saprobic and parasitic niches. This appears to be the case for some of the Verticillium wilts. Some ‘verticillium’ moulds are parasites, others feed on root exudes, and others can grade into true saprobes. Most of hitherto mentioned imperfect ‘genera’ are anamorph names. The teleomorphic names of the sexual forms are taxonomically more accurate. However, in many cases, the individual species are known only from their anamorphic states. Usually more than one genus occurs within each anamorphic type.

Many of the soil fungi live off of the sugary exudes of plant roots. These niches grade into the true mycorrhizae. Mycorrhizal fungi are actively symbiotic in that they aid plants' roots in the absorption of nutrients. These true mycorrhizae include such macro-fungi as the toadstools and the hypogeous truffles and tuckahoes.

References

Czederpiltz, Daniel L. Lindner; Volk, Thomas J.; Burdsall, Harold H., Jr. 2001. Field observations and inoculation experiments to determine the nature of the carpophoroids associated with Entoloma abortivum and Armillaria. Mycologia. 93(5): 841-851.

Freinkel, Susan. 2002. If all the trees fall in the forest ... Discover. 23 (12) 67-73.

Grubisha, L.C. Trappe, J.M. Molina, R. and Spatafora, J.W. 2001. Biology of the ectomycorrhizal genus Rhizopogon. V. Phylogenetic relationships in the Boletales inferred from LSU rDNA sequences. Mycologia 93(1): 82–89.

Hagen, Bruce W. 2001. Sudden Oak Death Part 1: symptoms, biology and potential impact. Arborist News. 10(6):29-31.

Heinrich, Bernd. 1997. The Trees in My Forest. Cliff Street Books. New York.

Holiday, Paul. 1989. A Dictionary of Plant Pathology. Cambridge University Press. New York. 140-141, 233-240.

Margulis, Lynn and Sagan, Dorian. 1995. What is Life? Simon & Schuster. New York.

Money, Nicholas, P. 2002. Mr. Bloomfield’s Orchard - the mysterious world of mushrooms, molds, and mycologists. Oxford University Press. New York.

Schwarze, F.W.M.R., Engels, J. and Mattheck, C. 2004. Fungal Strategies of Wood Decay in Trees. Springer. Berlin.

Thorn, R. Greg. 1991. Mushrooms of Algonquin Provincial Park. The Friends of Algonquin Park. Whitney Ontario.

Tudge, Colin. 2000. The Variety of Life. Oxford University Press. Oxford. 127-157.

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