284 
The size of the mat and its approximate 
distance from the ground were recorded. 
Three disks of mycelium, each 7 mm. in 
diameter, were cut from the mat with a 
cork borer. One disk was taken from the 
periphery of the mat, one from the edge 
of the central pad, and a third from a 
point approximately halfway between the 
other two. When perithecia were present, 
four additional disks, each 7 mm. in diam- 
eter, were taken with the cork borer from 
within the perithecium-producing “band” 
on four sides of the pad. Also, a small 
cross section of the central pad of each mat 
was taken with a knife. The cork borer 
and the knife blade were washed in alcohol 
and flamed before they were used in sam- 
pling a mat or pad. 
The three mycelial disks were placed in 
a sterile, 4-ounce glass bottle that con- 
tained moist filter paper. The perithecium 
samples taken from each mat were placed 
in the bottle with the mycelial disks from 
the same mat, but they were kept separated 
from the mycelium by folds in the filter 
paper. The pad samples from each mat 
were kept in a separate bottle for later de- 
termination of viability of inner cells. All 
bottles were stored in the iced picnic boxes 
for transportation to the laboratory. After 
samples had been taken from a mat, the 
bark was carefully returned to its original 
position and nailed down securely with 
small nails. 
Whole mats were removed from trees 
with a chisel in such a manner that with 
each was a piece of the wood beneath, ap- 
proximately one-half inch in_ thickness. 
The mats were placed separately in Lind- 
lene plastic film bags, most of them two- 
thirds quart size. These bags were then 
closed with small rubber bands, to hold in 
the moisture, and placed in an iced picnic 
box. 
Not all mats were sampled or collected 
when found. As it was suspected that the 
lifting of bark over a mat might hasten 
deterioration or drying of the fungus, some 
mats were tagged and, for various periods 
of time, left undisturbed. At 2-week in- 
spection intervals the bark was removed 
from these mats, several mats at each in- 
spection, and the condition of each com- 
pared with the condition of mats of the 
same age which had been sampled and left 
on the trees. The lifting of bark from 
ILttino1is NATURAL History SURVEY BULLETIN 
Vol. 26, Art. 3 
mats, and replacing it, did not noticeably 
hasten deterioration of the mats. 
Wood and Bark on Forest Floor 
It has been shown (Curl et al. 1952, 
1953) that the thick mycelial mats of 
Endoconidiophora fagacearum develop on 
wood and bark pieces cut from wilt-killed 
oaks in the mat-producing stage and dis- 
carded or placed on the forest floor. There- 
fore, this type of growth must be consid- 
ered as one of the possible sources of inoc- 
ulum from which the disease could be 
spread. 
The mat-producing stage of a _ wilt- 
killed tree may be described as the period 
of decline of the tree during which the 
bark is moderately loose and the wood be- 
neath is light reddish-brown in color and 
has a strong amyl acetate or ripe fruit 
odor characteristic for the fungus. Pre- 
liminary tests showed that the ability of 
the fungus to grow out of the wood and 
form macroscopic growth is closely re- 
lated to the presence of the ripe fruit odor. 
As wilt-killed trees in the study areas 
reached the mat-producing stage, pieces 
of bark and wood measuring approxi- 
mately 4 by 8 inches (the wood about an 
inch thick) were cut from the trunks 
where the ripe fruit odor was present. 
The bark and the wood were separated. 
The pieces of bark were placed, inner sur- 
faces down, and the pieces of wood were 
placed, outer surfaces down, on the forest 
floor in shaded places. New pieces were 
cut and laid down about every 2 weeks 
from November 1, 1952, to July 1, 1953, 
until the trees had deteriorated to such an 
extent that they ceased to have the odor 
that indicated presence of the fungus. 
Mats that developed on these pieces were 
sampled in the same manner as those on 
trees. 
Insect Collections 
Insects found on mycelial mats were col- 
lected at the same time that the mats were 
sampled. Adults and larvae were placed 
in small vials and temporarily stored in 
the metal iced picnic boxes. Mats that 
were examined and left on the trees af- 
forded a month-to-month opportunity to 
study insect populations occurring on mats 
of all ages. The influence of certain spe- 
