ually seven feet in
width. The width of the alley varies according to the mind of the owner,
from two to three or three and one-half feet. The narrow alley
economizes space in the structure of a house; the wide alley, while
slightly increasing the cost of the structure, makes it much more
convenient in handling the material, and in moving about the house. The
beds are constructed of one-inch boards. Various kinds of lumber are
used, the hemlock spruce, the oak, Georgia pine, and so on. The beds are
supported on framework constructed of upright scantling and cross
stringers upon which the bottom boards are laid. These occur at
intervals of three to four feet. The board on the side of each bed is 10
to 12 inches in width. The bottom bed, of course, is made on the ground.
The upper beds in the tier are situated so that the distance is about
three feet from the bottom of one bed to the bottom of the next above.
Figs. 228 to 231 show the general structure of the beds.

=Heating.=--One portion of the house is set apart for the boiler room,
where a small hot water heater is located. The position of the heater in
one of these houses is shown in Fig. 227. In other cases, where the
plant is quite a large one, a small separate or connecting boiler
apartment is often constructed. In other cases, where the house is
connected with or adjoining a system of greenhouses devoted to hothouse
vegetables, the water pipes may run from the general boiler house which
supplies the heat for all the houses. The water pipes in the mushroom
houses are sometimes run beneath the boards or the walk in the alley, or
in other cases are run just beneath the roof of the building.

=Cultivation of mushrooms under benches in greenhouses.=--This method is
practiced to quite a large extent by some growers. In the house of Mr.
William Swayne, Kennett Square, Pa., a number of large houses, devoted
through the winter to the growing of carnations, are also used for the
cultivation of mushrooms, a single long bed being made up underneath the
beds of carnations. In these houses the water pipes providing heat for
the building run along the sides of the building underneath the
carnation beds at this point. Under these beds, where the water pipes
run, no mushroom beds are made, since the heat would be too great, but
under the three middle rows of beds in the house, mushroom beds are
located. In this way, in a number of houses, several thousand square
feet of surface