282 
Fig. 2.—Typical crack in the bark of a 
growth of a fungus mat beneath the bark. 
gether as a mycelial mat. The mat varies 
in size from 1 by 1 cm. to 48 by 14 cm. 
The central pad is elongated oval to ellip- 
tical, dull green to black in color, and has 
a daedaloid surface. It is pseudoparen- 
chymatous in structure and is usually free 
of visible loose mycelium. 
The following arbitrary classification, 
based on the stage of development or de- 
cline, was given to the mycelial mats ex- 
amined in the study reported here. A mat 
of each class is shown in fig. 3. 
Class I. An immature or fresh mat, still 
in the rapid growth phase, with mycelium 
light tan or buff in color and having a 
firm, light- to dark-colored central pad 
which shows no sign of decline. 
Class I]. A mature mat, with mycelium 
and central pad beginning to darken 
slightly, the pad being firm and showing 
no definite signs of deterioration; vege- 
tative growth appearing to have ceased or 
nearly ceased. 
Class III. An aging mat, with mycelium 
and central pad becoming darker, the pad 
beginning to shrink or crack slightly from 
drying; showing other definite signs of 
aging but not deteriorating. 
I_tLinois NaturAL History SurvEY BULLETIN 
wilt-killed oak tree. 
Vol. 26, Art. 3 
The crack resulted from 
Class IV. A declining mat; mycelium 
and pad very dark or black, usually with 
only parts of the pad remaining intact; 
showing definite signs of rapid decline. 
Class V. A deteriorating mat and pad, 
having lost nearly all consistency and hav- 
ing been reduced to a mass of dry, or wet, 
black soil-like material. 
Methods of Field Sampling 
Trees in the five study areas were thor- 
oughly examined twice each month from 
October 1, 1952, to July 31, 1953. Some 
mats were examined and, after being sam- 
pled, were left on the trees. Others were 
removed from the trees and taken to the 
laboratory for study. Still others were 
tagged and left undisturbed for various 
periods of time. Metal picnic boxes 
equipped with ice containers were used for 
storing and transporting collected mate- 
rial from the field to the iaboratory. 
When the ice containers were kept filled 
with ice, the temperatures of the boxes 
were maintained below 16 degrees C., usu- 
ally between 5 and 12 degrees, even during 
the hottest days of summer. The time 
