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.
[Illustration: FIG. 28. IN THE MUSHROOM CAVES OF PARIS.]
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.
[Illustration: FIG. 29. GATHERING MUSHROOMS IN THE PARIS CAVES FOR
MARKET.]
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.