mber is
an important one, and the system of ridge beds avoids the expense of
this item of lumber. In other cases, where the flat beds are used with
the board supports, the cost of lumber is considered a small item when
compared with the additional labor involved in making the ridge bed. The
flat beds are very quickly made, and the material in some cases is not
more than 7 inches deep, allowing a large surface area compared with the
amount of food material, for the growth of the mushrooms. It may be
possible, with the flat, shallow bed system, that as many or more
mushrooms are obtained from the same amount of manure, as in the case of
the ridge beds. When we consider the cost of the manure in some places,
this item is one which is well worth considering.

THE HOUSE CULTURE OF MUSHROOMS.

Where this method of cultivation is employed, as the main issue, houses
are constructed especially for the purpose. In general the houses are of
two kinds. Those which are largely above the ground, and those where a
greater or lesser pit is excavated so that the larger part of the house
is below ground. Between these extremes all gradations exist. Probably
it is easier to maintain an equable temperature when the house is
largely below ground. Where it is largely above ground, however, the
equability of the temperature can be controlled to a certain extent by
the structure of the house. In some cases a wall air space is maintained
around the sides and also over the roof of the building. And in some
cases even a double air space of a foot or 18 inches each is maintained
over the roof. In some cases, instead of an air space, the space is
filled with sawdust, single on the sides of the house, and also a 12 or
18-inch space over the roof. The sides of the house are often banked
with earth, or the walls are built of stone or brick.

[Illustration: FIGURE 227.--Double mushroom house (L. S. Bigony's
Mushroom Plant.) Packing room at left, "curing" shed at right, next to
this is boiler room.]

All of these houses, no matter what the type of construction, require
ventilation. This is provided for by protected openings or exits through
the roof. In some cases the ventilators are along the side of the roof,
when there would be two rows of ventilators upon the single gable roof.
In other cases a row of ventilators is placed at the peak, when a single
row answers. These ventilators are provided with shut-offs, so that the
ventilation can be cont