Fungi: Their Nature and Uses

by M. C. Cooke

Berkeley, in Hooker’s “Journal of Botany,” vol. ii. (1843), p. 408.

XIV.

COLLECTION AND PRESERVATION.

The multitudinous forms which fungi assume, the differences of substance, and variability in size, render a somewhat detailed account of the modes adopted for their collection and preservation necessary. The habitats of the various groups have already been indicated, so that there need be no difficulty in selecting the most suitable spots, and as to the period of the year, this will be determined by the class of objects sought. Although it may be said that no time, except when the ground is covered with snow, is entirely barren of fungi, yet there are periods more prolific than others.[A] Fleshy fungi, such as the Hymenomycetes, are most common from September until the frosts set in, whereas many microscopic species may be found in early spring, and increase in number until the autumn.

The collector may be provided with an ordinary collecting box, but for the Agarics an open shallow basket is preferable. A great number of the woody kinds may be carried in the coat-pocket, and foliicolous species placed between the leaves of a pocket-book. It is a good plan to be provided with a quantity of soft bibulous paper, in which specimens can be wrapped when collected, and this will materially assist in their preservation when transferred to box or basket. A large clasp-knife, a small pocket-saw, and a pocket-lens will complete the outfit for ordinary occasions. In order to preserve the fleshy fungi for the herbarium, there is but one method, which has often been described. The Agaric, or other similar fungus, is cut perpendicularly from the pileus downwards through the stem. A second cut in the same direction removes a thin slice, which represents a section of the fungus; this may be laid on blotting paper, or plant-drying paper, and put under slight pressure to dry. From one-half of the fungus the pileus is removed, and with a sharp knife the gills and fleshy portion of the pileus are cut away. In the same manner the inner flesh of the half stem is also cleared. When dried, the half of the pileus is placed in its natural position on the top of the half stem, and thus a portrait of the growing fungus is secured, whilst the section shows the arrangement of the hymenium and the character of the stem. The other half of the pileus may be placed, gills downward, on a piece of black paper, and allowed to rest there during the night. In the morning the spores will have been thrown down upon the paper, which may be placed with the other portions. When dry, the section, profile, and spore paper may be mounted together on a piece of stiff paper, and the name, locality, and date inscribed below, with any additional particulars. It is advisable here to caution the collector never to omit writing down these particulars at once when the preparations are made, and to place them together, between the folds of the drying paper, in order to prevent the possibility of a mistake. Some small species may be dried whole or only cut down the centre, but the spores should never be forgotten. When dried, either before or after mounting, the specimens should be poisoned, in order to preserve them from the attacks of insects. The best medium for this purpose is carbolic acid, laid on with a small hog-hair brush. Whatever substance is used, it must not be forgotten by the manipulator that he is dealing with poison, and must exercise caution. If the specimens are afterwards found to be insufficiently poisoned, or that minute insects are present in the herbarium, fresh poisoning will be necessary. Some think that benzine or spirits of camphor is sufficient, but as either is volatile, it is not to be trusted as a permanent preservative. Mr. English, of Epping, by an ingenious method of his own, preserves a great number of the fleshy species in their natural position, and although valueless for an herbarium, they are not only very ornamental, but useful, if space can be devoted to them.

Leaf parasites, whether on living or dead leaves, may be dried in the usual way for drying plants, between folds of bibulous paper under pressure. It may be sometimes necessary with dead leaves to throw them in water, in order that they may be flattened without breaking, and then dry them in the same manner as green leaves. All species produced on a hard matrix, as wood, bark, etc., should have as much as possible of the matrix pared away, so that the specimens may lie flat in the herbarium. This is often facilitated in corticolous species by removing the bark and drying it under pressure.

The dusty Gasteromycetes are troublesome, especially the minute species, and if mounted openly on paper are soon spoiled. A good plan is to provide small square or round cardboard boxes, of not more than a quarter of an inch in depth, and to glue the specimen to the bottom at once, allowing it to dry in that position before replacing the cover. The same method should be adopted for many of the moulds, such as Polyactis, etc., which, under any circumstances, are difficult to preserve.

In collecting moulds, we have found it an excellent plan to go out provided with small wooden boxes, corked at top and bottom, such as entomologists use, and some common pins. When a delicate mould is collected on a decayed Agaric, or any other matrix, after clearing away with a penknife all unnecessary portions of the matrix, the specimen may be pinned down to the cork in one of these boxes. Another method, and one advisable also for the Myxogastres, is to carry two or three pill-boxes, in which, after being wrapped in tissue paper, the specimen may be placed.

A great difficulty is often experienced with microscopic fungi, such, for instance, as the Sphæriacei, in the necessity, whenever a new examination is required, to soak the specimen for some hours, and then transfer the fruit to a slide, before it can be compared with any newly-found specimen that has to be identified. To avoid this, mounted specimens ready for the microscope are an acquisition, and may be secured in the following manner. After the fungus has been soaked in water, where that is necessary, and the hymenium extracted on the point of a penknife, let it be transferred to the centre of a clean glass slide. A drop of glycerine is let fall upon this nucleus, then the covering glass placed over it. A slight pressure will flatten the object and expel all the superfluous glycerine around the edges of the covering glass. A spring clip holds the cover in position, whilst a camel-hair pencil is used to remove the glycerine which may have been expelled. This done, the edges of the cover may be fixed to the slide by painting round with gum-dammar dissolved in benzole. In from twelve to twenty-four hours the spring clip may be removed, and the mount placed in the cabinet. Glycerine is, perhaps, the best medium for mounting the majority of these objects, and when dammar and benzole are used for fixing, there is no difficulty experienced, as is the case with Canada balsam, if the superfluous glycerine is not wholly washed away. Specimens of Puccinia mounted in this way when fresh gathered, and before any shrivelling had taken place, are as plump and natural in our cabinet as they were when collected six or seven years ago.