MUSHROOM GROWING IN THE PARIS CAVES.

In caves and subterranean passages underneath the city of Paris and its environs, thousands of tons of mushrooms are artificially produced every year. These underground caves and tunnels are abandoned quarries from which white building stone and plaster have been excavated, and as the veins of stone permeated through the bowels of the earth, 40 to 125 feet deep, so were they quarried, and the blocks brought to the surface through vertical shafts. It is these tunnels, varying in height and width as the veins of stone varied, that are now used for mushroom-growing. M. Lachaume, in his book, The Cave Mushroom, tells us: "In the Department of the Seine there are 3000 quarries; those which have been abandoned and which are situated close to Paris at Montrouge, Bagneux, Vaugirard, MÉry, ChÂtillon, Vitry, Honilles, and St. Denis, are used by the 250 mushroom-growers of the Department. There are several of these quarries with horizontal galleries driven into the calcareous rock from the level of the road, which are mostly large enough to accommodate a good sized cart, but the majority can only be entered, like many coal mines, by vertical shafts 100 to 125 feet deep, down which everything has to pass. The laborers climb up and down a ladder, and the fresh manure is shoveled down the shaft from above, the waste stuff and mushrooms being hauled up in baskets from beneath by means of a windlass."

The manure used is obtained from the Paris stables and furnished by contractors, with whom the mushroom growers make special bargains because they are very particular about the kind and quality of the manure they use. Some of these growers use as much as 2000 to 3500 tons of manure each a year for their mushroom beds. To the caves in the immediate neighborhood of Paris the manure is hauled out in carts, but to MÉry and other places too far distant to be within easy carting distance it is sent by rail. The mushroom growers consider that the manure from animals that are worked hard and abundantly fed on dry, good food is the best; the droppings from these are always dry and rich in ammonia, nitrogen and phosphates. The manure from entire horses that are worked hard they regard as the best, and, next in value, that from mules. The manure from horses kept for pleasure, such as carriage and riding horses, is regarded as poor, notwithstanding the high feeding of these animals, and the manure from horses fed on grass or roots, also that of cows, as worthless. Stress is laid on the importance of having a good deal of urine-soaked straw in the manure, and this is another reason why manure from draught horses is preferred to that from animals kept for pleasure, as the bedding of the former is not apt to be kept so clean as that in aristocratic stables.

The preparation of the manure is conducted near the mouth of the caves or shafts on a level, dry piece of ground, and altogether out of doors. As soon as sufficient manure for a pile is obtained it is forked over, thoroughly shaken up and intermixed, divested of all extraneous matter such as sticks, stones, bottles, scrap iron, old shoes, and the like we find in city stable manure, and any dry straw is moistened with water. It is then squared off into a heap forty inches high and trodden down to thirty inches high. In this state it is left for about six days, when it is turned, shaken up loosely, the outside turned to the inside, and all dry parts watered; the same shallow square form is retained, and it is again trodden down firm. In about six days more it is again turned, shaken up, watered, squared off, and trodden as before. In about three days after this it should be fit for use and may be turned, shaken up loosely, and dumped down the shaft into the cave and carried to the spot where the beds are to be formed. Of course these operations must be modified according to circumstances and the condition of the manure.

In making the beds the ground is first marked off. The first bed is made alongside of the wall, and rounded to the front; the other beds run parallel with this and may be straight, crooked, or wavy, as the interior of the cave may suggest. The beds are all ridge-shaped, eighteen to twenty inches wide at the base, eighteen to twenty inches high in the middle, six inches wide at top, and the sides sloping. Pathways twelve inches wide run between the beds. The workmen build the beds by piece-work and receive one-half cent per running foot. A good workman can make 240 feet a day (Lachaume). The beds are built neatly and firmly and with much nicety as regards size and proportions. But the workmen do not use a fork or any other tool in the construction of the beds; they lift, shake up, spread and build the manure with their naked hands and pack it firm with their knees.

The spawn is obtained from the working beds and is what the mushroom growers there call "virgin" spawn, though not at all what we know by that term. As a succession of beds is kept up all the year round it is an easy matter for the growers to get their spawn at any time. The best time to get the spawn is when the young mushrooms are first appearing. A bed or part of a bed in capital working order is selected and broken up and the cakes of manure thoroughly matted up with the active mycelium are selected for spawning the fresh beds. It is asserted that from this active spawn crops of mushrooms appear in twenty days' less time than if dry spawn were used.

The French spawn is used. Somewhere between the seventh and fourteenth day after making the bed it will be in condition for spawning. Break the spawn into pieces between two and three inches long, two inches wide, and three-fourths of an inch thick, and insert these pieces in two rows along the sides of the ridges; the first row eight inches above the ground, the second row eight inches above the first, and the pieces put in quincunx fashion eight inches apart in the row. The manure is firmly packed in upon the spawn, the surface left smooth and even and without being further disturbed until earthing time.

Much stress is laid upon stratifying the spawn before using, when dry spawn is employed. About eight days before a bed is to be spawned the dry spawn is spread out in a row on the floor of the cave or cellar so that it may absorb moisture and the mycelium begin to run. At spawning time these cakes or flakes are broken up and used in the ordinary way, and, it is claimed, with a week's difference in favor of the early appearing of the mushrooms. But no more spawn than is necessary for immediate use should be stratified, for it will not bear being dried and damped again.

The chips and powder of the stone which has been taken out of the quarry and which can be had in abundance on the floor of the quarry or on the surface of the ground around the shaft, are sifted, and the finer part saved and mixed with earth in the proportion of three parts of stone dust to one of earth, and with this the beds are molded over. The powdered stone is strongly impregnated with salts, so advantageous to the mushrooms.

In seven to nine days after spawning, the beds are ready for earthing over. This depends upon the condition of the spawn and how well it has run in the manure. Before being earthed over the outside surface of the beds should be covered with white filaments radiating in all directions which give to the beds a bluish appearance. When the bed is in the proper state for being covered with earth the mold is laid on equally and firmly over the surface about three-fourths of an inch deep. It is then thoroughly watered through a fine-rosed watering pot and allowed to settle until the next day, when it is beaten solid by the back of a wooden shovel. The bed now needs no further care until the young mushrooms appear, except a light occasional watering should it get dry.

In spacious, high-roofed caves the mean temperature is about 52° F., while in narrow, low-roofed ones it is about 68°. Of course this makes a wide difference in the time of bearing and duration of the beds made in the different caves; those in the warm caves come into bearing sooner and stop bearing quicker than do those in the high-roofed caves. On an average the first mushrooms appear in about forty days after the beds are spawned, and the beds continue bearing for forty or sixty days, but toward the end of that time the yield diminishes very rapidly.

They are gathered once a day, usually about midnight, so that they may reach the Paris market early in the morning. In size the mushrooms range from three-fourths to one and five-eighths inches in diameter of top, and are pure white in color. The workmen always gather the mushrooms by plucking them out by the roots, and never by cutting them; the gatherers have two baskets, carried knapsack fashion on their back; one is to receive the mushrooms as they are picked, the other contains mold with which to fill in the little holes made by pulling the mushrooms out of the bed. In some caves one man gathers the mushrooms and leaves them in little piles on the bed as he goes along, a woman comes after him and places them in a basket, and a man follows her and fills up the holes with earth. Before bringing the mushrooms up out of the caves they are covered over with a cloth to avoid contact with the outer air, which is apt to turn them brown. They are then placed in baskets that contain twenty-three to twenty-five pounds and sent to market, where they are sold at auction as they arrive. Or they may be sent to preserved-vegetable manufacturers, who contract for them at an all round price.

Proper ventilation is regarded as being of great importance, not only for the sake of the workmen, but also for the mushrooms, which will not thrive in an impure atmosphere. Ventilation is afforded by means of narrow shafts surmounted by tall wooden chimneys whose upper ends are cut at an angle so that the beveled side faces north. In order to avoid sudden changes of temperature and strong draughts, fires, trap doors, and other means employed in assisting the ventilation of coal mines are adopted. To stop strong draughts, too, in the passages, tall, straw-thatched hurdles are set up. In narrow caves the breath of the workmen, the gases given off by fermentation, and the products of combustion of the lamps would soon so vitiate the atmosphere as to render the caves uninhabitable were they not properly ventilated. Indeed, it frequently occurs that caves in which mushrooms have been grown continuously for some years have to be abandoned for a year or two because the crop has ceased to prosper in them. But after they have been thoroughly cleared of all beds and the surface soil that would have been likely to be touched or affected by the manure, and ventilated and rested for a year or two, mushrooms can again be grown in them successfully.