400 
AMERICAN JOURNAL OF BOTANY 
[V0I..10, 
invaded by the mycelium and a little decayed, and in the other they were 
badly decayed and partly dried. Blocks were tested against both dry and 
moist heat, the moist heat being obtained by supporting the blocks over 
water in a sealed Mason jar which was placed in the drying oven beside the 
blocks subjected to dry heat. The blocks to be tested with dry heat were 
removed from the flasks and air-dried in a warm room for several days, 
since otherwise, being wet inside, they would for a few hours in reality 
have been subjected to a moist heat. The blocks to be tested with moist 
heat were taken fresh from the culture flasks and tested in their partially 
moist condition. For the tests, the blocks were cut transversely in half, 
each yielding two pieces J by f by 1 inch in size. A sufficient number of 
blocks were placed in the oven at the beginning of the test, and one was 
removed at the end of each desired interval from 12 hours up to several 
days, varying with the temperature. 
The viability of the mycelium within the block after being subjected to 
heat was tested by cultures made from the individual blocks. These 
cultures were made in a culture case kept swabbed with HgCl 2 , with instru¬ 
ments dipped in alcohol and flamed, upon a block of wood similarly treated. 
The outer part of the block was flamed, and a slice was removed from each 
of the six sides. From the remaining inner part, ten pieces of wood material 
were put in as many tubes of malt agar and set aside to incubate. At least 
six weeks were allowed for the viable mycelium within the wood to grow out 
upon the agar. 
Results 2 
The results are given in tables 1 and 2 and text figure 1. Inasmuch as 
little difference was observed between the behavior of mycelium from old 
and of that from new cultures, the differences are not compiled here. In a 
few instances, blocks from fresh cultures gave growth where those from old 
ones did not; in one case the situation was reversed, and in others there 
was no difference. It was to be expected that some irregularities would 
occur. For instance, Lenzites sepiaria produced no growth at 50° C. moist 
heat, but one tube of the ten in two tests at 52 0 C. showed growth. Again, 
at 52 0 C. moist heat, old mycelium of Lentinus lepideus showed growth after 
36 hours’ exposure in the first test, but two repetitions with old and one with 
fresh mycelium failed to show growth. In some tests there might be growth 
from the block exposed 48 hours and none from the one exposed 36 hours. 
In the case of the vigorous Lenzites trabea at 48° C. moist heat, one test 
gave no growth at all at 12 hours, while a repetition with blocks from the 
same culture showed that 24 hours’ exposure did not kill the fungus. In 
the main, however, the results were reasonably uniform. 
2 Some preliminary results were presented in a paper read before the American Wood 
Preservers’ Association (7). At that time it was pointed out that certain of the periods 
at the lower temperatures, with dry heat (60 percent and 70 percent more particularly), 
were thought to be incorrect and repetitions were to be made. These questioned tests have 
been repeated and the discrepancies between the curves in the two papers are thus explained. 
