An introduction to poroide fungi
9. Practical advice for collection and determination of polypores
A set of field equipment for collecting polypores should preferably include the following:
Field book or labels to put with the specimens
Pencils or pens
Sturdy knife with sheath
Paper bags or envelopes made of newspaper
Equipment needed for collection of polypores is simple and inexpensive. As most are wood-rotting fungi, a small hand axe or knife is needed. This enables the collector to remove basidiocarps with a minimum of damage and makes it easy to obtain samples of the substratum and the associated rot. A strong knife is necessary and indispensible for removing specimens from beneath logs or other locations where an axe cannot be used. A hook with a handle is extremely useful for rolling logs. Such hooks are readily available from suppliers of logging equipment and provide enough leverage to move surprisingly large logs. It is useful to paint the handle of the axe or the sheath of the knife in bright colours. Too often they are lost when moving from one place to another, and bright colours are of great help in finding them again. We speak from long and partly bitter experience!
In the forest there are two methods for handling the specimens. Some prefer to wrap each one individually in a sheet of newspaper and mark it with a symbol for the host from which the sample was collected. The other method is to use larger paper bags and place 3-5 samples in them, and mark the host on the bag or place a leaf or needle of the host inside. The samples can then be sorted when coming back to the cabin or the laboratory. In some cases it will also be useful to take a little of the wood on which the specimen was growing to ascertain the type of rot.
A hand lens is indispensible and should be kept on a string around your neck, otherwise it will soon be lost. In the field it is wise to carry a cheap one, because whatever you do, sooner or later you will leave it on a log or stump. The type used by stamp collectors is often sufficient for field use.
Annual basidiocarps of many species have a high percentage of water when fresh and consequently will shrink considerably on drying. In addition, changes in colour and consistency commonly occur. Notes on fresh specimens and photographs should be routinely made before specimens are dried. Most of the perennial basidiocarps change little on drying but it is wise to make notes on these in the fresh condition also.
Before putting the samples on the drier, a small tag with the collecting number should be placed under each one. For large perennial specimens it is wise to cut them up in slices cut radially to make drying faster and also for easier storing.
Basidiocarps of pileate polypores usually develop on standing trees or stumps or on exposed surfaces of fallen trees or branches – they are often conspicuous and easy to find.
A large number of polypores have basidiocarps that are resupinate. These effused basidiocarps commonly develop on the underside of fallen trees and are inconspicuous and easily overlooked unless logs are turned over.
To the collector of wood rotting fungi, rolling over a large log at the height of the fruiting season is an exciting experience akin to opening a Christmas present. When conditions for fruiting of wood-rotting fungi are really good, any red-blooded mycologist working with these fascinating organisms finds it difficult to quit as long as one more log remains to be rolled over.
Spore prints should be made on a rough black paper or a microscopic slide since the spores of most polypores are white in masses. Spore prints on such paper can be stored with the specimens in the herbarium for many years without yellowing or other deterioration.
Select a good specimen with well-developed tubes and carefully cut off a portion that will fit on a piece of paper. Smaller specimens are used intact. Write the collection number of the specimen on the spore print paper. Invert the specimen with tubes down on the paper and wrap the specimen and spore print paper in waxed paper or put it under a glass jar or similar device. Many perennial species can be induced to sporulate if the specimens are wrapped in wet newspaper for 8 to 12 hours and then placed under a closed container. Carefully place it so that the tubes are as vertical as possible. Polypore basidiocarps, particularly those with tubes of small diameter, must be oriented properly or no spores will reach the paper to leave a print. Spore prints can be obtained during the course of the day's field work. However, it is difficult to keep the spore print specimens properly oriented under these conditions. Spore prints of agarics, and clavaroid, corticioid, and hydnaceous fungi are much easier to obtain because they do not require as precise orientation as do polypores.
Preservation of specimens
Drying is the simplest method of preserving polypore specimens. Basidiocarps should be dried over a heater, preferably an electric forced air dryer with fan and heating coil. In other situations a gas heater will provide an excellent heat source. A dryer equipped with screen shelves to promote easy circulation of air should be used. For field work a collapsible dryer can be constructed for use with an electric or a gas powered heat source.
Specimens should be placed in the dryer with the field label placed in such a position that it will not be lost or become associated with the wrong collection. One efficient method is to place specimen and label in an open mesh bag at the time of collection. The specimens can then be dried in the mesh bags.
Small specimens can be left in paper bags for drying. After drying they should be placed in paper bags with the field label for temporary storage. The most commonly used driers in Europe these days are of the type used for drying fruits, edible fungi or vegetables. They are available from many hardware or kitchen equipment shops.
Many polypores, especially those of genera like Trametes, Pycnoporus and Ganoderma are susceptible to infection from insects, especially beetles. These often survive drying at fairly high temperature for days, and can destroy a collection if not checked. The most efficient and cheapest way is to place the dried specimen in a deep freezer for about a week at a temperature of about -15 to -25° C.
Most freezers will achieve this when set at the lowest temperature. Much of the effect comes from the very quick drop in temperature, i.e. from 20°C to -20°C or lower. This gives the insects no time to prepare for hibernation which is important for their successful survival through a normal winter.
Storage and arrangement of fungaria
Polypores can usually be stored without difficulty as they are rather tough and hard when dry. Today it is common to store all specimens in plastic bags with a seal along the top edge.
Some fungaria prefer to store collections inside larger boxes with each species separated by a small piece of cardboard or similar material. The boxes are more expensive, but admit more collection per unit than loose sheets on which the bags or envelopes either are glued or placed loose.
It is always a problem how to place the species in a fungarium so that specimens can be retrieved easily for examination. If taxonomy had been stabilized one could put the specimens according to genera and then either place the genera alphabetically or in groups according to relationship, i.e. families like Ganodermataceae etc. If a card-file is kept up to date, this will be a satisfactory system.
The problem arises in larger fungaria where specimens may be filed by people without knowledge of the group. Specimens may then easily be misplaced as the generic name used on the label may well not be the same as used in the fungarium.
The alternative is to place all polypores alphabetically according to specific epithet. The latter is fairly stabilized in Europe as only very minor changes can be expected. Such a system makes it very easy to find and file specimens even for non-mycologists. However, the system has the disadvantage that closely related species may be placed in different parts of the fungarium. Based on how these advantages and disadvantages are considered one or another system should be adopted.
With some experience many polypores can be named on sight, but often a microscopical examination is necessary to reach a reliable determination, as is especially the case with resupinate specimens.
For a microscopical examination specimens should be sectioned along the tubes. Pore mouths are mostly sterile and a fertile hymenium is found a certain distance beyond the pore mouths where spores and possibly cystidia may be observed.
A small slice of the context or pileal cover may be mounted in the same preparation. The sectioning may be done with any sharp thin tool; personally we prefer a razor blade. The best results are achieved if the sectioning is done under a stereo-microscope.
If a phase-contrast microscope is available, the sections may be mounted in 3-5% KOH. This medium makes it easy to squash the preparation with a gentle tap on the cover glass. Hyphae, cystidia and spores can then normally be examined without difficulty.
If a phase-contrast microscope is not available, sections of light-coloured polypores should be stained with Cotton blue, Congo red, etc. (for instructions, see below). Cotton blue in lactic acid is often used, and spores and hyphae are said to be cyanophilous if their walls take colour. However, a certain precaution is necessary as protoplasm very often takes up colour. To the untrained eye, it can be difficult to distinguish a real cyanophilous reaction and just a colouration of the protoplasm. Thus, a cyanophilous reaction is not used as a diagnostic character in this manual, but is mentioned in a few cases where it is a prominent factor.
An iodine reaction is most commonly noticed with Melzer's reagent. Spores and hyphae are said to be amyloid if they become grey or blue and dextrinoid if they turn reddish brown. A negative reaction with this reagent is noted as IKI-.
In dense polypores, sections often contain entrapped air which can be difficult to remove, but a drop of ethyl alcohol will solve the problem. A drop of mounting medium is then placed on the sections just before the alcohol evaporates.
Reagents for staining
Cotton blue: Cotton blue in 60% lactic acid.
Congo red: 1% Congo red in conc. ammonia.
0.5 g Iodine, 1.5 g KI, 22 g Chloral
hydrate and 20 g water.
Eosin and Phloxine: 1 g Eosine or Phloxine in 100 g water.
Lactophenol: (to clarify preparations) 5 g lactic acid,
5 g phenol, 10 g glycerine and 5 g water.
KOH: 2-5% KOH in water.