Читать книгу Collins Mushroom Miscellany - Patrick Harding - Страница 14

King Alfred’s cakes Daldinia concentrica, growing on ash

{John & Sue Buckingham/NHPA}

We can find the answer to this question on the Beatles’ classic 1960s’ album Revolver, where they sang:

Here, there and everywhere.

Although the distribution of larger fungi, especially those referred to as mushrooms and toadstools, is not quite as extensive as it is for many of the less conspicuous, smaller fungi, the range of habitats that include at least some members of the fungal kingdom is enormous. Fungi, unlike plants, cannot make their own organic matter, so their distribution is largely limited by the availability of materials that they can utilise as fungal food. Some habitats, such as woodlands, contain substantial amounts of potentially available organic matter, whereas others, including the world’s oceans, are less favourable. Despite this, oceans are far from devoid of fungi, although most of the species that can put up with the saline conditions are microfungi.

The average amateur mycologist, especially one with a culinary interest, concentrates on finding fruitbodies of the larger fungi including the agarics (mushrooms and toadstools), bracket fungi, puffballs and morels. For mycologists, knowledge of the habitat requirements of sought-after species is comparable to the way in which botanists and ornithologists are able to predict which flowers or birds they may find when visiting a particular habitat.

Common species of mushroom and toadstool include those that are relatively catholic in their taste, but also those species that are restricted to a specific food source that is itself widely available. Rare species often demand exacting habitat requirements that are themselves uncommon. Other rare fungi may be limited by environmental factors such as temperature or water availability. In Britain the latter group are frequently at the edge of a wider distribution throughout mainland Europe.

Dung roundhead (Stropharia semiglobata) is a very common ‘little brown job’ that grows on the weathered dung of a wide range of herbivores, including cow, sheep, horse and rabbit. It is found in pastures, heaths and even in woodland. It also grows on land fertilised with herbivorous dung and on clifftop grassland, where its normal requirement for animal dung is fulfilled by bird guano.

In contrast, the nail fungus (Poronia punctata), an ascomycete with fruitbodies that are shaped like a nail or golf tee, only grows on horse dung and is virtually restricted in Britain to the New Forest where it grows on dung of semi-wild ponies. It is one of the fungal species with a UK Biodiversity Action Plan (see here). Until the early part of the 20th century horses, their dung and the nail fungus were all common. In the 21st century, even in those parts of Europe, including Britain, where horses are still kept for riding, the fungus is now very rarely found. It appears that the use of additives in horse feedstuffs and the use of artificial fertilisers on the pastures grazed by horses have affected the nature of horse dung, something that has not happened to dung from the less pampered ponies grazing on the largely unimproved land of the New Forest.

Agaric fruitbody emerging through tarmac

{Joe Blossom/NHPA}

Sulphur tuft (Hypholoma fasciculare) is one of the commonest toadstools to be found on the decayed wood of tree stumps, fallen trunks and timber used to make path steps or edging for garden borders. It grows on a very wide range of different tree species, both broadleaved and coniferous; just as its substrate is common so is the fungus. As the common name implies, it grows in dense tufts and, when young, has a sulphur-yellow cap, stem and gills, the latter turning purplish-brown as the spores mature. Sadly, this very frequent fungus is not edible as it has a very bitter taste, comparable to quinine.

Birch polypore (Piptoporus betulinus) is nearly as common as sulphur tuft, despite being restricted to birch trees. This is because birch trees are very common in Britain and the fungus, which is a parasite on living trees, can continue to live as a saprophyte on dead ones. In contrast, oak polypore (Piptoporus quercinus) is rare enough to need protection in a manner similar to that for the nail fungus. It grows on dead wood in the trunks of veteran oaks, usually ancient deer park or forest trees (often over 400 years old) that were formerly pollarded. Unlike young birches, the number of veteran oaks is very limited and so too, as a result, is the oak polypore.

The distribution and frequency of many woodland fungi are strongly influenced by their need for very specific habitats. Fungi that form mycorrhizal associations with tree roots (see here) often do so with only one or a limited number of tree species. Examples include the larch bolete (Suillus grevillei), associated with larch trees, and beech milkcap (Lactarius blennius), which is only rarely found away from beech trees. Some species obtain their food from tree fruits, including ear pick fungus (Auriscalpium vulgare), a small toadstool that grows only on partially buried pine cones. Other more common fungi feed on the discarded leaf litter that is a feature of deciduous woodland. Typical of these is wood woollyfoot (Collybia peronata).

Larch bolete –Suillus grevillei

{Laurie Campbell/NHPA}

Fungi of grassland communities include field mushroom (Agaricus campestris) and species such as yellow fieldcap, previously known as egg-yolk fungus (Bolbitius titubans, was B. vitellinus), which feed on decayed grass leaves, dung and straw. Some 50 species of waxcap (Hygrocybe spp.) are largely restricted to old, unlimed, grazed pasture that has not had inorganic fertiliser added. This is a habitat whose area has declined by over 90% since 1930. Mown, unfertilised old lawns and even some cemeteries are also homes for waxcaps and other species that are unable to compete in grassland where lime and inorganic fertilisers have been applied.

Other habitats that include fungi specific to them include coastal dune systems, where such rarities as the dune stinkhorn (Phallus hadriani) and dune mushroom (Agaricus devoniensis) are to be found. The fruitbodies of dune mushroom develop under the sand, only pushing through as the spores mature; possibly a strategy to cut down on water loss in what is a very dry environment.

A strange group of fungi grows on burnt ground associated with bonfires, forest fires and the controlled or accidental burning of heather moorland. Such ‘phoenicoid’ fungi (as in phoenix-like, literally arising from the ashes) include the beautiful tiger’s eye or brown goblet (Coltricia perennis), a bracket fungus with a mushroom shape that is occasionally used in florists’ displays. Tiger’s eye also grows in other sites, especially on sandy, acidic soil. In contrast bonfire scalycap (Pholiota highlandensis), a brown toadstool, is restricted to fire sites in either woodland or heathland. Despite this limitation it is common and widespread, as are fire sites. It is often found with bonfire inkcap (Coprinus jonesii), which is only rarely found away from burnt ground. Several cup or disc-like ascomycete fungi inhabit fire sites, where the ground may be covered with their fruitbodies. One of these is the stalked bonfire cup (Geopixis carbonaria).

Geopixis is occasionally found protruding from the mortar of garden walls or emerging from damp plaster inside houses. Both these sites are very alkaline (they have a high pH) because of their lime content. The fresh ash resulting from wood or heathland fires is also extremely alkaline, one reason why fresh ash should not be used as a garden mulch. Very few fungi or plants can thrive in such conditions, but it appears that many phoenicoid fungi are adapted to and even thrive in an environment that is toxic to other species.

A relative of Geopixis is even more at home in our homes. Cellar cup (Peziza cerea) produces clumps of delicate, pale buff-coloured, cup-shaped fruitbodies up to 3–4cm across. It grows on damp mortar or earth in moist cellars and erupts from rotting sandbags (an increasingly common habitat in flood-prone areas). It is famous for its association with toilets, where the moist conditions of gentlemen’s urinals, or on a wall or carpet soaked by a leaking cistern may result in large numbers of the fruitbodies. Fortunately, cellar cup does little damage and may even be a useful indicator of the damp conditions on which it thrives. Such conditions may provide a foothold for a much more serious household fungus and one that is not found outside any artificial habitat in Britain; dry rot (Serpula lacrymans) (see here).

Gardens, along with parks, playing fields and churchyards, provide important urban sites for mushrooms and toadstools. Mycorrhizal species (see here) that obtain their food from tree roots are common in gardens and parks, and even on pavements. Earthballs (Scleroderma spp.) frequently burst through tarmac or thrust up between paving stones. Toadstools that are mycorrhizal with garden trees include a range of boletes, especially red cracking bolete (Boletus chrysenteron) and species of milkcap (Lactarius) and brittlegill (Russula). Not all of these require mature trees; woolly milkcap (Lactarius torminosus) may form fairy rings around birch trees that are no more than 10 years old.

Parasitic fungi species that parasitise and kill both trees and shrubs have more serious consequences for gardeners and park keepers. One such toadstool is honey fungus, which in older books went under the name Armillaria mellea and whose destructive nature is outlined in Chapter Twenty-two. Lawns are home to many species known as ‘little brown jobs’, of which brown mottlegill or hay cap (Panaeolina foenisecii) is the most common. This poisonous toadstool is not infrequently devoured by inquisitive young children and also by dogs, but the outcome is rarely serious, if worrying for parents and pet owners. I was pleased to find magic mushroom (Psilocybe semilanceata) growing on my own back lawn (see here), but lawn fanatics, along with bowling and golf green keepers are less enamoured of fairy ring fungus (Marasmius oreades), which often disfigures the turf on which it grows (see here).

As the organic, recycling movement has spread so the garden compost heap has made a comeback. Microfungi and bacteria are responsible for the breakdown of organic waste, a process that may cause the compost to reach temperatures as high as 60°C. Such conditions are only tolerated by thermophilic (heat-loving) toadstools including some species of inkcap (Coprinus spp.). Older heaps are occasionally colonised by wood blewit (Lepista nuda), whose mauve-gilled fruitbodies are edible and excellent; a bonus for the organic gardener. The use of woodchip on paths and as a garden mulch has ‘mushroomed’ in the past 20 years, bringing with it a range of toadstools not previously encountered in gardens or anywhere else in Britain (see here). Equally, the growing of exotic plants in heated greenhouses and conservatories has resulted in increased sightings of tropical fungi in Britain. Among the most conspicuous of these is plantpot dapperling or yellow parasol (Leucocoprinus birnbaumii), a bell-shaped little toadstool recognised by its bright yellow, scurfy cap with a distinctly grooved margin. Its first European record, in the early part of the 19th century, was in Prague Botanic Garden.

Another relatively new habitat has provided a novel home for a previously unusual British fungus. This is the very beautiful split-gill (Schizophyllum commune). Looking like a small furry bracket fungus from above, the underside reveals a fan-like, coralloid mass of branching gills. Most British records up until the middle of the 20th century came from south-eastern England, where it grows on fallen wood (especially beech) exposed to the sun. By the start of the 21st century I had begun to find it in the Peak District, possibly an example of a move northwards under the influence of climate change. As a thermophilic species it is more common in tropical regions, but it has now found a new home in Britain; plastic-wrapped bales of hay. The mycelium grows on the warm contents of the bags and its fruitbodies emerge through the plastic lining.

Wood blewit– Lepista nuda

{Laurie Campbell/NHPA}

In 2002 the same fungus made headlines with its ability to grow in another warm place: the human body. ‘Fatal Fungus that Preys on Humans’ was the title for one newspaper story. The fungus mycelium has been found to cause mouth ulcers and toenail infections; hardly fatal, but the fungus can be much more of a problem for people suffering from a suppressed immune system, including those infected with HIV or anyone taking immunosuppressant drugs.

Given that, unlike green plants, mushrooms and toadstools do not require light for the maintenance of their nutrition, it should come as no surprise that caves and old mines have been, and still are, used to grow edible mushrooms. In France the ordinary white mushrooms are still known as Paris mushrooms from the time when they were only cultivated in old mines beneath Paris. A number of fungi occur naturally in such habitats, including some microfungi that are not found anywhere else. Of the larger fungi growing in old mines, some species attack wooden pit props, such as the mine fungus (Antrodia vaillantii), a bracket fungus that also rots wooden greenhouses and has even been recorded growing on wet coke. Dry rot (Serpula lacrymans) also occurs in mines, where it may assume unusual growth forms (see here).

A small number of toadstools obtain their food by growing on, or in close proximity with, the fruitbodies of other fungi. Parasitic bolete (Pseudoboletus parasiticus) is a small yellow-brown-capped bolete that is occasionally found growing from the base of fruitbodies of common earthball (Scleroderma citrinum). As its name implies, it has long been presumed to be parasitic on the earthball, but some researchers believe that it only requires the presence of the earthball to stimulate fruiting and is not a parasite. Similar doubts surround the rare piggyback rosegill (Volvariella surrecta), which I have only seen once in the past 30 years when I found clusters of the toadstool emerging from the decaying remains of some clouded agarics (Clitocybe nebularis). The rosegill could be a parasite or live only on the dead fruitbodies of clouded agaric; it has never been found in any other situation. The well-known yellow brain (Tremella mesenterica), a jelly fungus that brightens old stems of gorse and other shrubs through the winter, has now been found to be parasitic on the mycelium of another fungus within the twig. Life is not always what it seems.

Microfungi occupy many more habitats than do the larger mushrooms and toadstools. These include both fresh and salt water. British examples of the former that have come to public attention are fish moulds, one of which causes black patches and the untimely death of many a pet goldfish, and another which results in the death of salmon. Fungi also attack insects, including house flies, and the honeycomb of hive bees. Plant parasites include the rust fungi which, along with mildews and related ‘moulds’, cause immense damage in both horticulture and agriculture. Microfungi cause food spoilage and also kill trees, although the fungus that has left its mark by killing elm trees is in fact an ascomycete, but with tiny fruitbodies that are rarely seen (see here).

Bread mould–Rhizopus stolonifera, scanning electron micrograph of a sporangium

{Jeremy Burgess/NHPA}

Humans provide an unwelcome home for fungi in the form of ringworm and thrush. Some fungi have even caused eye infections in contact lens solutions. Species of Malassezia, tiny yeast-like fungi, are present on our skin where they feed on the oily products of our sebaceous glands. These fungi can cause dermatitis and more commonly the shedding of skin flakes; so even dandruff can be blamed on fungi. Other microfungi result in the brown foxing seen in old books, the etching of the glass in cameras and field glasses, and the spoiling of the surface of CDs.

Perhaps most intriguing of all is the fungus that ‘eats’ jet and diesel fuel. Oil is, of course, an organic material, being composed of the long-dead remains of marine organisms, so it should come as no surprise that a range of microfungi has been detected in oil-based fuels. The most important of these is the creosote fungus Amorphotheca resinae, which not only breaks down creosote (which has been used as a preservative against fungi) but can also feed on jet fuel (kerosene) as long as at least a little water (ten parts of water per million of fuel is enough) is available. Empty tanks are vulnerable to condensation in humid conditions and this can provide the necessary water. High-flying aircraft experience very low temperatures, but the creosote fungus can put up with temperatures down to –25°C. The greatest danger to planes and their passengers comes from the fungal mycelium, which may block filters and small pipes, thus preventing fuel flow to an engine.

As with all fungi, preventing the initial infection is one way of limiting damage. Many years ago I was told a story by someone who had worked for the RAF. He recounted a big NATO exercise involving jet planes from different countries which, as part of the training, were refuelled in mid-air from special tanker planes. Only later was it discovered that one tanker plane was infected with creosote fungus and, in a manner analogous to the transmission of sexual disease, the fungus had been passed on in the refuelling process. Expensive decontamination was required. The same fungus can also live on diesel (contaminated with water), resulting in fuel blockage in cars and lorries. Fungi really are ‘Here, there and everywhere’.