414 
Journal of Agricultural Research 
Vol. XXIX, No. 8 
Table I .—Viability experiments 
Medium 
Date in¬ 
oculated 
Date tested 
Time elapsed 
Observations (dupli¬ 
cate tubes) 
Oatmeal agar_ 
Dec. 31,1919 
Jan. 26,1920 
Feb. 25,1920 
Sept. 8,1921 
_do _ 
Aug. 25,1920 
7 months, 25 days. 
7 months _. 
Alive in one tube. 
Alive in both tubes. 
Do 
Dead in both tubes. 
Alive in one tube. 
Dead in both tubes. 
Do. 
Do. 
Do. 
Alive in both tubes. 
Alive in one tube. 
Dead in both tubes. 
Do 
Potato agar_ 
Do... 
_do_ 
6 months. . _ 
Oatmeal agar__ 
Aug. 22,1921 
_do _ 
11 months, 14 days. 
_do _ 
Corn-meal agar.... 
Congo Red agar.____ 
_do_ _ 
_do . _ . 
_ do _. 
Beef agar...___ 
_do_ 
_do_ 
_do _ 
Potato agar_ 
.do _ 
_do__. 
_ .do _. 
Potato dextrose agar__ 
.do _ 
_do_ 
__do ___ 
Carrot agar___ 
_do.. 
_do__. 
_do .. ... 
Bean agar__ 
_do_ _ 
_do_ 
_do _ 
SteameTl rice__ 
Apr. 14,1920 
Apr. 17,1920 
_do_ 
-—do_- 
16 months, 8 days. _ 
16 months, 5 days.. 
Sterilized geranium stem_ 
The experiments indicate viability 
after eleven and a half months at room 
temperature on carrot agar, bean agar, 
and corn-meal agar; and after seven 
and nearly eight months on potato 
6° 11° 14°16°I8° 23° Z7° 
0° 5° 10° 15° 20° 25° 
DEGREES CENTIGRADE 
agar and oatmeal agar, respectively. 
The fungus was not recovered after il 
to 16 months on seven other media 
used. Viability appears to be con¬ 
nected largely with the water-retaining 
power of the media. 
Death occurred much 
sooner on plate cultures, 
where the large surface 
and thin layer of medium 
leads to rapid desiccation. 
On October 8,1923, sterile 
tap water was poured over 
corn-meal agar plate cul¬ 
tures 3 and 6 months old 
and bone dry. Absorp¬ 
tion and softening soon 
took place, but no ger¬ 
mination of the numerous 
oospores and sporangia 
was observed after three 
days, nor did growth oc¬ 
cur on replacing the water 
with fresh cornmeal agar. 
Stock cultures in oat¬ 
meal agar tubes have, 
however, been kept in the 
icebox for 18 months 
without loss of viability. 
TEMPERATURE RELA¬ 
TIONS 
The Figure 3 outlines 
the growth curves aver¬ 
aged from two experi¬ 
ments with plates in ice 
thermostats and warm 
incubators, ranging from 
2° to 37.5° C. Triplicate 
plates of corn-meal agar 
were placed in each com¬ 
partment and measure¬ 
ments of the colony 
diameter were made at 
24-hour intervals. Inoc¬ 
ulations were made from 
a 3-day-old corn-meal 
Fig. 3. 
-Graphs showing colony diameters at 2°- 37.5° C. for 24 and 
48 hours 
agar plate, which was cut 
up into one-sixteenth inch 
