Oct., 1923] 
SNELL — EFFECT OF HEAT UPON FUNGI 
409 
long to kill it. The effect of the same temperatures at intermediate humid¬ 
ities can not be determined. 
These results are taken to apply only to i-inch stock, but with longer 
periods of treatment of larger material the results should be the same. 
Moist wood is a fairly good conductor of heat. Furthermore, there is in 
most cases a sufficient margin between the time necessary to kill the 
mycelium in i-inch stock and the time that even the i-inch lumber is exposed 
to killing temperatures to allow heat to penetrate to the center of large 
material and to act upon any mycelium. Most of the decay in structural 
timbers without doubt owes its incipiency to infection between the time of 
cutting and the time of installation. These results indicate that kiln-drying 
could be counted upon to render structural timbers sterile internally as far 
as most if not all wood-destroying fungous mycelium is concerned, and that 
in kiln-drying we have an important agent in combating decay in buildings. 
Bearing of the Results upon the Possible Sterilizing Effect of 
Wood-preservation Processes 
The results given in this paper indicate also that various wood-preserva¬ 
tion processes should be sterilizing processes as well. The necessity for 
sterilizing treated wood is not everywhere understood. It is often noted 
that treated wood decays inside in the untreated portion leaving a hollow 
shell which has been protected. This decay within may have started in 
two ways. The fungi may have entered through checks or nail holes, etc., 
i.e ., through breaks in the protecting preserved layer, or it may have arisen 
from fungous, mycelium which entered the wood between the time of felling 
of the tree and the time of preservative treatment. It is certain that a 
great deal of decay in structural timber owes its origin to this method of 
infection, as already pointed out. Hence, it is important that the inside of 
the treated timbers should be sterilized, as otherwise the preservative treat¬ 
ment may be a waste of time and money. This discussion, of course, 
advocates the treatment of wood already infected only in the sense that all 
timber apparently sound may be and in a great many cases probably is 
infected with fungous mycelium before it is installed, and refers only to 
those preservative treatments in which a fairly high degree of heat is applied. 
This is very different from even suggesting any kind of preservative treat¬ 
ment, with or without heat, for wood already visibly infected or partially 
decayed. 
Wherever heat is applied, either in a preliminary seasoning treatment or 
in the preserving process itself, it is possible that the heat will be sufficient 
to kill any fungi within the wood. It may make some difference whether or 
not the wood is green or partially dry. If the wood is green, or is wet 
enough so that the air in the wood cells will be saturated, the heat applied 
will react as moist heat, and the amount of heat necessary for sterilization 
purposes under these conditions is not great, since 55 0 C. for 12 hours will 
