ter.
Side window ventilators are not necessary, at the same time they are
useful in the early part of the season and in summer time; they should
be double and tightly packed in winter. The walls, if made of brick,
should be hollow, if of wood, double; indeed, walls built as if for an
ice house are the very best for a mushroom house, and should be banked
with earth, tree leaves, or strawy manure in winter, to help keep the
interior of the house a little warmer.

[Illustration: FIG. 8. SECTION OF MRS. C. J. OSBORNE'S MUSHROOM HOUSE.]

The floor should be perfectly dry; that is, so well drained that water
will not stand upon it, but it is immaterial whether the floor is an
ordinary earthen one or of wood or cement.

[Illustration: FIG. 9. GROUND PLAN OF MRS. OSBORNE'S MUSHROOM HOUSE.]

The roof should be double and always sloping,--never flat. The hoar
frost that appears in severe weather inside a single roof is likely to
melt as the heat of the day increases, and this cold drip falling upon
the beds below is very prejudicial to the mushroom crop. A double roof
saves the beds from this drip, and it also renders the house warmer, and
less fire is needed to maintain the requisite temperature. One might
think that a single roof like that of a dwelling house, and then a flat
ceiling under it, would be equivalent to a double sloping roof, but it
is not. The moisture arising from the interior of the house condenses
upon the flat ceiling, and the water, having no way of running off,
drips down upon the beds. With a sloping ceiling or inside roof the
water runs down the ceiling to the walls. A very pointed example of this
may be seen in Mrs. C. J. Osborne's excellent mushroom house at
Mamaroneck, N. Y. It had been built in the most substantial manner, with
a sloping roof and a flat ceiling under the roof, but so much annoyance
was caused by the drip falling from it upon the beds below that her
gardener had the flat ceiling removed and a sloping one built instead,
and now it works splendidly, and a few months ago I saw as fine a crop
of mushrooms in that house as one could wish to look at.

The interior arrangement of the mushroom house may resemble that of the
mushroom cellar. Beds may be made alongside of the walls and, if there
is room, also along the middle of the house, and shelves erected in the
same way as in the cellar. But in the case of cold, thin outside walls,
the shelf-beds should not be built close against them, b