242 



STUDIES OF AMERICAN FUNGI. 





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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 

 i8-inch space over the roof. The sides 

 of the house are often banked with earth, 

 or the walls are built of stone or brick. 



All of these houses, no matter what 

 the type of construction, require venti- 

 lation. 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 controlled at will. The size of the 

 house varies, of course, according to the 

 extent of the operations which the grower 

 has in mind. 



The usual type of house is long and 

 rather narrow, varying from 50 to 150 

 feet long by 18 to 21 or 24 feet wide. In 

 some cases the single house is constructed 

 upon these proportions, as shown by Fig. 

 226, with a gable roof. If it is desired to 

 double the capacity of a house, two such 

 houses are built parallel, the intercepting 

 wall supporting the adjacent roof of the 

 two houses, as shown in Fig. 227. A still 

 further increase in the capacity of the * 

 house is often effected by increasing the 

 number of these houses side by side. 

 This results in a series of 8 or 10 houses 

 forming one consolidated block of houses, 



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