The cultivation of fungi in this country for esculent purposes is confined to a single species, and yet there is no reason why, by a series of well-conducted experiments, means should not be devised for the cultivation of others, for instance, Marasmius orcades, and the morel. Efforts have been made on the Continent for the cultivation of truffles, but the success has hitherto been somewhat doubtful. For the growth of the common mushroom, very little trouble and care is required, and moderate success is certain. A friend of ours some years since was fortunate enough to have one or two specimens of the large puff-ball, Lycoperdon giganteum, growing in his garden. Knowing its value, and being particularly fond of it when fried for breakfast, he was anxious to secure its permanence. The spot on which the specimens appeared was marked off and guarded, so that it was never desecrated by the spade, and the soil remained consequently undisturbed. Year after year, so long as he resided on the premises, he counted upon and gathered several specimens of the puff-ball, the mycelium continuing to produce them year after year. All parings, fragments, &c., not utilized of the specimens eaten were cast on this spot to rot, so that some of the elements might be returned to the soil. This was not true cultivation perhaps, as the fungus had first established itself, but it was preservation, and had its reward. It must be admitted, however, that the size and number of specimens diminished gradually, probably from exhaustion of the soil. This fungus, though strong, is much approved by many palates, and its cultivation might be attempted. Burying a ripe specimen in similar soil, and watering ground with the spores, has been tried without success.[A]

As to the methods adopted for cultivation of the common mushroom, it is unnecessary to detail them here, as there are several special treatises devoted to the subject, in which the particulars are more fully given than the limits of this chapter will permit.[B] Recently, M. Chevreul exhibited at the French Academy some splendid mushrooms, said to have been produced by the following method: he first develops the mushrooms by sowing spores on a pane of glass, covered with wet sand; then he selects the most vigorous individuals from among them, and sows, or plants their mycelium in a cellar in a damp soil, consisting of gardener’s mould, covered with a layer of sand and gravel two inches thick, and another layer of rubbish from demolitions, about an inch deep. The bed is watered with a diluted solution of nitrate of potash, and in about six days the mushrooms grow to an enormous size.[C] The cultivation of mushrooms for the market, even in this country, is so profitable, that curious revelations sometimes crop up, as at a recent trial at the Sheriffs’ Court for compensation by the Metropolitan Railway Company for premises and business of a nurseryman at Kensington. The Railway had taken possession of a mushroom-ground, and the claim for compensation was £716. It was stated in evidence that the profits on mushrooms amounted to 100 or 150 per cent. One witness said if £50 were expended, in twelve months, or perhaps in six months, the sum realized would be £200.

Immense quantities of mushrooms are produced in Paris, as is well known, in caves, and interesting accounts have been written of visits to these subterranean mushroom-vaults of the gay city. In one of these caves, at Montrouge, the proprietor gathers largely every day, occasionally sending more than 400 pounds weight per day to market, the average being about 300 pounds. There are six or seven miles’ run of mushroom-beds in this cave, and the owner is only one of a large class who devote themselves to the culture of mushrooms. Large quantities of preserved mushrooms are exported, one house sending to England not less than 14,000 boxes in a year. Another cave near FrÉpillon was in full force in 1867, sending as many as 3,000 pounds of mushrooms to the Parisian markets daily. In 1867, M. Renaudot had over twenty-one miles of mushroom-beds in one great cave at MÉry, and in 1869 there were sixteen miles of beds in a cave at FrÉpillon. The temperature of these caves is so equal that the cultivation of the mushroom is possible at all seasons of the year, but the best crops are gathered in the winter.

Mr. Robinson gives an excellent account, not only of the subterranean, but also of the open-air culture of mushrooms about Paris. The open-air culture is never pursued in Paris during the summer, and rarely so in this country.[D] What might be termed the domestic cultivation of mushrooms is easy, that is, the growth by inexperienced persons, for family consumption, of a bed of mushrooms in cellars, wood-houses, old tubs, boxes, or other unconsidered places. Even in towns and cities it is not impracticable, as horse-dung can always be obtained from mews and stables. Certainly fungi are never so harmless, or seldom so delicious, as when collected from the bed, and cooked at once, before the slightest chemical change or deterioration could possibly take place.

Mr. Cuthill’s advice may be repeated here. He says:—“I must not forget to remind the cottager that it would be a shilling or two a week saved to him during the winter, if he had a good little bed of mushrooms, even for his own family, to say nothing about a shilling or two that he might gain by selling to his neighbours. I can assure him mushrooms grow faster than pigs, and the mushrooms do not eat anything; they only want a little attention. Addressing myself to the working classes, I advise them, in the first place, to employ their children or others collecting horse-droppings along the highway, and if mixed with a little road-sand, so much the better. They must be deposited in a heap during summer, and trodden firmly. They will heat a little, but the harder they are pressed the less they will heat. Over-heating must be guarded against; if the watch or trial stick which is inserted into them gets too hot for the hand to bear, the heat is too great, and will destroy the spawn. In that case artificial spawn must be used when the bed is made up, but this expedient is to be avoided on account of the expense. The easiest way for a cottager to save his own spawn would be to do so when he destroys his old bed; he will find all round the edges or driest parts of the dung one mass of superior spawn; let him keep this carefully in a very dry place, and when he makes up his next bed it can then be mixed with his summer droppings, and will insure a continuance and excellent crop. These little collections of horse-droppings and road-sand, if kept dry in shed, hole, or corner, under cover, will in a short time generate plenty of spawn, and will be ready to be spread on the surface of the bed in early autumn, say by the middle of September or sooner. The droppings during the winter must be put into a heap, and allowed to heat gently, say up to eighty or ninety degrees; then they must be turned over twice daily to let off the heat and steam; if this is neglected the natural spawn of the droppings is destroyed. The cottager should provide himself with a few barrowfuls of strawy dung to form the foundation of his bed, so that the depth, when all is finished, be not less than a foot. Let the temperature be up to milk heat. He will then, when quite sure that the bed will not overheat, put on his summer droppings. By this time these will be one mass of natural spawn, having a grey mouldy and thready appearance, and a smell like that of mushrooms. Let all be pressed very hard; then let mould, unsifted, be put on, to the thickness of four inches, and trodden down hard with the feet and watered all over; and the back of a spade may now be used to make it still harder, as well as to plaster the surface all over.”[E] Mushrooms are cultivated very extensively by Mr. Ingram, at Belvoir, without artificial spawn. There is a great riding-house there, in which the litter is ground down by the horses’ feet into very small shreds. These are placed in a heap and turned over once or twice during the season, when a large quantity of excellent spawn is developed which, placed in asparagus beds or laid under thin turf, produces admirable mushrooms, in the latter case as clean as in our best pastures.[F]

Other species will sometimes be seen growing on mushroom-beds besides the genuine mushroom, the spawn in such cases being probably introduced with the materials employed. We have seen a pretty crisped variety of Agaricus dealbatus growing in profusion in such a place, and devoured it accordingly. Sometimes the mushrooms will, when in an unhealthy condition, be subject to the ravages of parasitic species of mould, or perhaps of Hypomyces. Xylaria vaporaria has, in more than one instance, usurped the place of mushrooms. Mr. Berkeley has received abundant specimens in the Sclerotioid state, which he succeeded in developing in sand under a bell glass. Of course under such conditions there is much loss. The little fairy-ring champignon is an excellent and useful species, and it is a great pity that some effort should not be made to procure it by cultivation. In Italy a kind of Polyporus, unknown in this country, is obtained by watering the Pietra funghaia, or fungus stone, a sort of tufa impregnated with mycelium. The Polypori, it is said, take seven days to come to perfection, and may be obtained from the foster mass, if properly moistened, six times a year. There are specimens which were fully developed in Mr. Lee’s nursery at Kensington many years since. Another fungus is obtained from the pollard head of the black poplar. Dr. Badham says that it is usual to remove these heads at the latter end of autumn, as soon as the vintage is over, and their marriage with the vine is annulled; hundreds of such heads are then cut and transported to different parts; they are abundantly watered during the first month, and in a short time produce that truly delicious fungus Agaricus caudicinus, which, during the autumn of the year, makes the greatest show in the Italian market-places. These pollard blocks continue to bear for from twelve to fourteen years.

Another fungus, which Dr. Badham himself reared (Polyporus avellanus), is procured by singeing, over a handful of straw, a block of the cob-nut tree, which is then watered and put by. In about a month the fungi make their appearance, and are quite white, of from two to three inches in diameter, and excellent to eat, while their profusion is sometimes so great as entirely to hide the wood from whence they spring.[G] It has been said that Boletus edulis may be propagated by watering the ground with a watery infusion of the plants, but we have no knowledge of this method having been pursued with success.

The culture of truffles has been partially attempted, on the principle that, in some occult manner, certain trees produced truffles beneath their shade. It is true that truffles are found under trees of special kinds, for Mr. Broome remarks that some trees appear more favourable to the production of truffles than others. Oak and hornbeam are specially mentioned; but, besides these, chestnut, birch, box, and hazel are alluded to. He generally found Tuber oestivum under beech-trees, but also under hazel, Tuber macrosporum under oaks, and Tuber brumale under oaks and abele. The men who collect truffles for Covent Garden Market obtain them chiefly under beech, and in mixed plantations of fir and beech.[H]

Some notion may be obtained of the extent to which the trade of truffles is carried in France, when we learn that in the market of Apt alone about 3,500 pounds of truffles are exposed for sale every week during the height of the season, and the quantity sold during the winter reaches upwards of 60,000 pounds, whilst the Department of Vaucluse yields annually upwards of 60,000 pounds. It may be interesting here to state that the value of truffles is so great in Italy that precautions are taken against truffle poachers, much in the same way as against game poachers in England. They train their dogs so skilfully that, while they stand on the outside of the truffle grounds, the dogs go in and dig for the fungi. Though there are multitudes of species, they bring out those only which are of market value. Some dogs, however, are employed by botanists, which will hunt for any especial species that may be shown to them. The great difficulty is to prevent them devouring the truffles, of which they are very fond. The best dogs, indeed, are true retrievers.

The Count de Borch and M. de Bornholz give the chief accounts of the efforts that have been made towards the cultivation of these fungi. They state that a compost is prepared of pure mould and vegetable soil mixed with dry leaves and sawdust, in which, when properly moistened, mature truffles are placed in winter, either whole or in fragments, and that after the lapse of some time small truffles are found in the compost.[I] The most successful plan consists in sowing acorns over a considerable extent of land of a calcareous nature; and when the young oaks have attained the age of ten or twelve years, truffles are found in the intervals between the trees. This process was carried on in the neighbourhood of Loudun, where truffle-beds had formerly existed, but where they had long ceased to be productive—a fact indicating the aptitude of the soil for the purpose. In this case no attempt was made to produce truffles by placing ripe specimens in the earth, but they sprang up themselves from spores probably contained in the soil. The young trees were left rather wide apart, and were cut, for the first time, about the twelfth year after sowing, and afterwards at intervals of from seven to nine years. Truffles were thus obtained for a period of from twenty-five to thirty years, after which the plantations ceased to be productive, owing, it was said, to the ground being too much shaded by the branches of the young trees. It is the opinion of the Messrs. Tulasne that the regular cultivation of the truffle in gardens can never be so successful as this so-called indirect culture at Loudun, but they think that a satisfactory result might be obtained in suitable soils by planting fragments of mature truffles in wooded localities, taking care that the other conditions of the spots selected should be analogous to those of the regular truffle-grounds, and they recommend a judicious thinning of the trees and clearing the surface from brushwood, etc., which prevents at once the beneficial effects of rain and of the direct sun’s rays. A truffle collector stated to Mr. Broome that whenever a plantation of beech, or beech and fir, is made on the chalk districts of Salisbury Plain, after the lapse of a few years truffles are produced, and that these plantations continue productive for a period of from ten to fifteen years, after which they cease to be so.

M. Gasparin reported to the jurors of the Paris Exhibition of 1855, concerning the operations of M. Rousseau, of Carpentras, on the production of oak truffles in France. The acorns of evergreen and of common oaks were sown about five yards apart. In the fourth year of the plantation three truffles were found; at the date of the report the trees were nine years old, and over a yard in height. Sows were employed to search for the truffles. Although these plantations consist both of the evergreen and common oak, truffles cannot be gathered at the base of the latter species, it so happening that it arrives later at a state of production. The common oak, however, produces truffles like the evergreen oak, this report states, for a great number of the natural truffle-grounds at Vaucluse are planted with common oaks. It is remarked that the truffles produced from these are larger but less regular than those of the evergreen oak, which are smaller, but nearly always spherical. The truffles are gathered at two periods of the year; in May only white truffles are to be found, which never blacken and have no odour; they are dried and sold for seasoning. The black truffles (Tuber melanosporum) commence forming in June, enlarging towards the frosty season; then they become hard, and acquire all their perfume. They are dug a month before and a month after Christmas. It is also asserted that truffles are produced about the vine, or at any rate that the association of the vine is favourable to the production of truffles, because truffle-plots near vines are very productive. The observation of this decided M. Rousseau to plant a row of vines between the oaks. The result of this experiment altogether does not appear to have been by any means flattering, for at the end of eight years only little more than fifteen pounds were obtained from a hectare of land, which, if valued at 45 francs, would leave very little profit. M. Rousseau also called attention to a meadow manured (sic) with parings of truffles, which was said to have given prodigious results.

The cultivation of minute fungi for scientific purposes has been incidentally alluded to and illustrated in foregoing chapters, and consequently will not require such full and particular details here. Somewhat intermediately, we might allude to the species of Sclerotium, which are usually compact, externally blackish, rounded or amorphous bodies, consisting of a cellular mass of the nature of a concentrated mycelium. Placed in favourable conditions, these forms of Sclerotium will develop the peculiar species of fungus belonging to them, but in certain cases the production is more rapid and easy than in others. In this country, Mr. F. Currey has been the most successful in the cultivation of Sclerotia. The method adopted is to keep them in a moist, somewhat warm, but equable atmosphere, and with patience await the results. The well-known ergot of rye, wheat, and other grasses may be so cultivated, and Mr. Currey has developed the ergot of the common reed by keeping the stem immersed in water. The final conditions are small clavate bodies of the order SphÆriacei, belonging to the genus Claviceps. The Sclerotium of the Eleocharis has been found in this country, but we are not aware that the Claviceps developed from it has been met with or induced by cultivation. One method recommended for this sort of experiment is to fill a garden-pot half full of crocks, over which to place sphagnum broken up until the pot is nearly full, on this to place the Sclerotia, and cover with silver sand; if the pot is kept standing in a pan of water in a warm room, it is stated that production will ensue. Ergot of the grasses will not always develop under these conditions, but perseverance may ultimately ensure success.

A species of Sclerotium on the gills of dead Agarics originates Agaricus tuberosus, another Agaricus cirrhatus,[J] but this should be kept in situ when cultivated artificially, and induced to develop whilst still attached to the rotten Agarics. Peziza tuberosa, in like manner, is developed from Sclerotia, usually found buried in the ground in company with the roots of Anemone nemorosa. At one time it was supposed that some relationship existed between the roots of the anemone and the Sclerotia. From another Sclerotium, found in the stems of bulrushes, Mr. Currey has developed a species of Peziza, which has been named P. Curreyana.[K] This Peziza has been found growing naturally from the Sclerotia imbedded in the tissue of common rushes. De Bary has recorded the development of Peziza Fuckeliana from a Sclerotium of which the conidia take the form of a species of Polyactis. Peziza ciborioides is developed from a Sclerotium found amongst dead leaves; and recently we have received from the United States an allied Peziza which originated from the Sclerotia found on the petals of Magnolia, and which has been named Peziza gracilipes, Cooke, from its very slender, thread-like stem. Other species of Peziza are also known to be developed from similar bases, and these Fuckel has associated together under a proposed new genus with the name of Sclerotinia. Two or three species of Typhula, in like manner, spring from forms of Sclerotium, long known as Sclerotium complanatum and Sclerotium scutellatum. Other forms of Sclerotium are known, from one of which, found in a mushroom-bed, Mr. Currey developed Xylaria vaporaria, B., by placing it on damp sand covered with a bell glass.[L] Others, again, are only known in the sclerotioid state, such as the Sclerotium stipitatum found in the nests of white ants in South India.[M] From what is already known, however, we feel justified in the conclusion that the so-called species of Sclerotium are a sort of compact mycelium, from which, under favourable conditions, perfect fungi may be developed. Mr. Berkeley succeeded in raising from the minute Sclerotium of onions, which looks like grains of coarse gunpowder, a species of Mucor. This was accomplished by placing a thin slice of the Sclerotium in a drop of water under a glass slide, surrounded by a pellicle of air, and luted to prevent evaporation and external influences.[N]

As to the cultivation of moulds and Mucors, one great difficulty has to be encountered in the presence or introduction of foreign spores to the matrix employed for their development. Bearing this in mind, extensive cultivations may be made, but the conditions must influence the decision upon the results. Rice paste has been used with advantage for sowing the spores of moulds, afterwards keeping them covered from external influences. In cultivation on rice paste of rare species, the experimenter is often perplexed by the more rapid growth of the common species of Mucor and Penicillium. Mr. Berkeley succeeded in developing up to a certain point the fungus of the Madura Foot, but though perfect sporangia were produced, the further development was masked by the outgrowth of other species. In like manner, orange juice, cut surfaces of fruits, slices of potato tubers, etc., have been employed. Fresh, horse-dung, placed under a bell glass and kept in a humid atmosphere, will soon be covered with Mucor, and in like manner the growth of common moulds upon decayed fruit may be watched; but this can hardly be termed cultivation unless the spores of some individual species are sown. Different solutions have been proposed for the growth of such conditions as the cells which induce fermentation, to which yeast plants belong. A fly attacked by Empusa muscÆ, if immersed in water, will develop one of the SaprolegniÆ.

The Uredines and other epiphyllous Coniomycetes will readily germinate by placing the leaf which bears them on damp sand, or keeping them in a humid atmosphere. Messrs. Tulasne and De Bary have, in their numerous memoirs, detailed the methods adopted by them for different species, both for germination of the pseudospores and for impregnating healthy foster plants. The germination of the pseudospores of the species of Podisoma may easily be induced, and secondary fruits obtained. The germination of the spores of Tilletia is more difficult to accomplish, but this may be achieved. Mr. Berkeley found no difficulty, and had the stem impregnated as well as the germen. On the other hand, the pseudospores of Cystopus, when sown in water on a slip of glass, will soon produce the curious little zoospores in the manner already described.

The sporidia of the Discomycetes, and some of the SphÆriacei, germinate readily in a drop of water on a slip of glass, although not proceeding further than the protrusion of germ-tubes. A form of slide has been devised for growing purposes, in which the large covering glass is held in position, and one end of the slip being kept immersed in a vessel of water, capillary attraction keeps up the supply for an indefinite period, so that there is no fear of a check from the evaporation of the fluid. Even when saccharine solutions are employed this method may be adopted.

The special cultivation of the Peronosporei occupied the attention of Professor De Bary for a long time, and his experiences are detailed in his memoir on that group,[O] but which are too long for quotation here, except his observations on the development of the threads of Peronospora infestans on the cut surface of the tubers of diseased potatoes. When a diseased potato is cut and sheltered from dessication, the surface of the slice covers itself with the mycelium and conidiiferous branches of Peronospora, and it can easily be proved that these organs originate from the intercellulary tubes of the brown tissue. The mycelium that is developed upon these slices is ordinarily very vigorous; it often constitutes a cottony mass of a thickness of many millimetres, and it gives out conidiiferous branches, often partitioned, and larger and more branched than those observed on the leaves. The appearance of these fertile branches ordinarily takes place at the end of from twenty-four to forty-eight hours; sometimes, nevertheless, one must wait for many days. These phenomena are observed in all the diseased tubercles without exception, so long as they have not succumbed to putrefaction, which arrests the development of the parasite and kills it.

Young plants of the species liable to attack may be inoculated with the conidia of the species of Peronospora usually developed on that particular host, in the same manner that young cruciferous plants, watered with an infusion of the spores of Cystopus candidus, will soon exhibit evidence of attack from the white rust.

It is to the cultivation and close investigation of the growth and metamorphoses of the minute fungi that we must look for the most important additions which have yet to be made to our knowledge of the life-history of these most complex and interesting organisms.