EVALUATION OF WOOD PRESERVATIVES 



135 



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Fig. 2— Soil -block cultures on the shelves in the incubation room The un- 

 painted wood shelves come to equilibrium with the temperature and relative 

 humidity and thus are a factor in keeping the conditions stable. Ihe back ea^es 

 of the shelves are set away from the wall to provide spaces for air circulation. iHe 

 front edges of the shelves are provided with metal labeling strips. 



