410 VEGETABLE FORCING 
Fig. 149.—A New Jersey double duty house. Mushrooms are grown in the cellar 
and plants and flowers in the greenhouse above. 
12 to 20 feet, but many of the modern ones are of much 
greater width, and they may be hundreds of feet in length. 
The most economical use of the space is to construct 
tiers of beds. The old houses seldom contained more 
than two or three beds, while some of the new ones have 
as many as five beds. Most growers prefer single beds of 
about 3 feet or double ones of 6 or 7 feet in width. (See 
Fig. 150.) The alleys should be at least 2 feet wide, and 
many of them allow more space, for the convenient 
handling of manure and other material. When the tiers 
contain several beds, each 8 to 10 inches deep, provision 
must be made for strong supports; 2 by 4 and 2 by 6 
scantling are generally employed, or heavy gas pipe 
makes a stronger, more durable and more sanitary frame, 
and the boards are easily removed at any time the beds 
are not in use. 
Mushrooms are grown in a few large caves in America. 
Pits, small caves, cellars and barns are often used by 
amateur growers. Florists and sometimes vegetable 
gardeners grow mushrooms under greenhouse benches. 
In fact, any place can be used which provides proper 
cultural conditions, with special reference to heat and 
moisture. There must be perfect drainage and the tem- 
