404 
AMERICAN JOURNAL OF BOTANY 
[Vol. io. 
that the available heat for sterilizing purposes throughout a roof plank, 
for instance, would be much less than that indicated as supplied. 
From the practical point of view, the following conclusions may be 
drawn: 
1. Dry heat in buildings in which the air is not artificially humidified is of 
no use for purposes of sterilizing wood infected with the five fungi discussed 
here. Too high a degree of heat for too long periods is necessary even in the 
small blocks to attain the end desired. A heating system in a building is 
capable of raising the temperature to only about 52 0 C. (125 0 F.), and such a 
temperature would not accomplish the sterilization. If automatic sprinklers 
are present, a temperature higher than 46° C. (115 0 F.) would not be safe. 
2. Dry heat in dry structures applied for the purpose of drying out the 
wood and thus preventing or retarding decay is highly to be recommended. 
Much timber enters a structure in a partially green condition, and such 
timbers are especially susceptible to decay. A thorough drying before 
occupation would prevent decay such as often takes place when green or 
wet lumber is installed. A preliminary drying before painting timbers on 
the interior of buildings would be good insurance against decay. Green 
or wet timbers may be expected to decay rapidly in a moist atmosphere 
unless proper precautions are taken, but they often decay in dry buildings 
because they are painted over when wet inside. They then rot during the 
retarded drying and may become a total loss before sufficiently dried. For 
buildings which are already slowly decaying, a periodic application of dry 
heat as high and for as long a period as possible would dry the wood and 
retard the destruction. 
3. Dry heat in structures of moist occupancy (really moist heat as ex¬ 
plained above) would have to be applied as high as obtainable for periods 
longer than two days to accomplish anything. We speak of two days 
because that is the time during which heat might be applied in operating 
structures —from Saturday noon until Monday morning. From text figure 1, 
it is seen that temperatures from 44 0 to 50° C. (112 0 to 122 0 F.) killed the 
mycelium in the small blocks, but it is certain that not only would it take 
more heat for larger timbers, but also so much heat would be radiated that 
more would be necessary than is shown by the graph. Hence, the applica¬ 
tion of dry heat even in structures where the humidity is high cannot be 
recommended under ordinary conditions, and it is not certain that long 
periods of application would be of more value in eliminating these fungi. 
4. Moist heat as such (humidified heat or free steam) need not be con¬ 
sidered here. In a dry structure, it would be necessary to apply the moist 
heat for a period sufficient for the moisture to permeate the wood before the 
killing action took effect, and this would not be practicable under ordinary 
conditions. Secondly, dry heat applied to wet wood such as is found in 
weave sheds means that the fungi are in any case being subjected to moist 
heat within the wood. 
