June, 1955 
decline, while the wood was still green 
and the bark very tight. The other trees 
had already started to produce mats be- 
fore they were cut. 
Tree H-4 did not produce mats at any 
time. The bark loosened very slowly, and 
the fungus odor could never be detected 
in the wood. Tree P-6 did not produce 
mats until late in March, 1953, 5 months 
after it had been felled. “Thirteen large 
mats were found on this tree up to May 5, 
after which no new mats were found. 
Twenty mats were found on tree R-8 at 
the time of cutting, and 14 additional 
mats appeared over a period of almost 5 
months. The last mats to form on this 
tree were found on March 23, 1953. 
Tree R-7 had 10 mats when felled and 
produced only 1 more, which was found 
on April 21, 1953. Tree R-6 had 7 mats 
2 weeks prior to being felled, 23 mats 
were present at the time of felling, and 
only 2 developed while the tree lay on the 
ground, these appearing in the early part 
of June, 1953. 
After trees, whether felled or standing, 
ceased to produce new mats, the fungus 
sometimes could still be isolated from 
wood where the characteristic odor per- 
sisted. Where this odor could no longer 
be detected, the fungus cou!d not be iso- 
lated. 
Stimulation in Mat Production 
Environmental Conditions.—From 
the time of the initial appearance of mats 
on a tree to the time when no further 
mat development occurred, the number of 
new mats varied from month to month. 
As each of the 30 trees used in these stud- 
ies was examined every 2 weeks, all new 
mats that had formed since the previous 
examination were counted and _ tagged, 
fig. 13. It is believed that few, if any, 
mats with cracks* were missed; mats with 
cracks too small to be seen were located 
by the bark-tapping method. 
The data in table 10 show the numbers 
of new mats found per month on individ- 
ual trees, the total number of mats found 
on each tree during the 10-month study 
period, and the total number found per 
* Except where otherwise specified, all mats included 
in these studies were typical mycelial mats with cen- 
tral pads and associated with cracks in the bark of in- 
fected trees. 
Curt: Oak Witt INocuLa 301 
13.—Wilt-killed oak 
10-inches 
d.b.h., marked with tags to show positions of 
mycelial mats. This tree was in a study area 
in northern Illinois. 
Fig. 
tree, 
