296 
spores stored at 0 degrees was represented 
by a line that was nearly straight, while 
decreases in germinability of spores stored 
at other temperatures were represented by 
lines that showed abrupt decreases be- 
tween time intervals. 
Ten to 20 days after the last spore ger- 
mination was observed, cultures of Endo- 
conidiophora fagacearum were obtained, 
from mass transfers to potato dextrose 
agar, of fungus from the labels that were 
stored at 25, 31, and 34 degrees under 
both dry and humid conditions. Possibly 
these cultures resulted from a few still 
viable spores that could have been missed 
in the last germination test, or trom some 
other part of the fungus that might have 
remained alive. 
Treatment of Samples From Nature 
Conidia.—Each set of three mycelial 
disk samples that had been taken from 
mats in the field was placed in a 10-ml. 
sterile water blank and_ thoroughly 
crushed and stirred with a glass rod to set 
the spores free in suspension. The approx- 
imate number of spores in 1 ml. of the 
suspension was determined with a Spencer 
Bright-Line counting chamber. This 
number divided by 3 gave the average 
number of spores in 1 ml. of water pro- 
vided by a single disk sample 7 mm. in 
diameter. The suspension was then ad- 
justed to about 300,000 spores per ml., 
and single drops were placed on the sur- 
face of water agar. The plates were in- 
cubated at 28 degrees for 36 hours and 
the per cent of germination determined 
from a count of 300 spores. The mycelial 
disks sometimes provided fewer than 300,- 
000 spores per ml. of suspension, in which 
cases the suspensions were plated in their 
original concentrations, and as many 
spores as could be found up to 300 were 
counted. 
Mats that were collected whole in the 
field were sampled in the laboratory with 
a cork borer, as described on page 284. 
Approximate numbers of conidia and their 
germinability were determined as de- 
scribed in the paragraph above. 
Perithecia and Ascospores.—Peri- 
thecia were counted with the aid of a 
glass slide, one end of which was marked 
with black ink into several areas, each 
Intinotis NarurAL History Survey BULLETIN 
Vol. 26, Art. 3 
measuring 6 mm. square. The slide was 
placed on the surface of a mycelial disk 
or whole mat and viewed through a binoc- 
ular microscope. In the case of disk sam- 
ples, counts were made of all perithecial 
necks seen within two to four of the 
square areas marked on the slide. In the 
case of whole mats, similar counts were 
made on each of four slides of the central 
pad. The average number of perithecia 
in a 6 mm. square area of surface was de- 
termined for each whole mat and for each 
mat represented by disks. 
From each perithecium-bearing mat, ex- 
uding masses of ascospores were picked at 
random from about 15 perithecial necks 
with a dissecting needle and stirred thor- 
oughly in the well of a hanging-drop slide 
which contained sterile distilled water. 
Drops of the suspension were planted on 
water agar and incubated for spore ger- 
mination as described for conidia. Data 
obtained are presented in the section titled 
“Availability of Fertile Perithecia,” be- 
ginning on page 315. 
Mycelial Pads.—Interior parts of all 
pads and portions of pads that were col- 
lected in the field were transferred to po- 
tato dextrose agar to determine the via- 
bility of their cells. The plates were in- 
cubated at 25 degrees for 7 days. The re- 
sults are given in table 22. 
Further Treatment of Mats.—After 
the germinability of conidia and ascospores 
was determined, approximately 100 mats, 
involving all classes of condition shown in 
fig. 3, were placed in plastic film bags 
containing moist cotton; about half of 
them were stored at 12 and the rest at 16 
degrees to determine their ability to re- 
new vegetative growth. Renewed growth 
occurred only occasionally around the 
margins of immature mats and on parts 
of the wood pieces that had no growth 
previous to being stored. Most of the 
mats were overrun rapidly by contaminat- 
ing fungi and bacteria. 
Twenty-eight immature (class I) and 
mature (class II) mats were stored in the 
laboratory to determine the longevity of 
conidia and pad cells when mats are pro- 
tected from natural environmental condi- 
tions. Some of these mats were placed in 
plastic bags with wet cotton and others 
were wrapped in dry paper toweling. 
They were then stored, some at 8 de- 
