182 
IOWA ACADEMY OP SCIENCE 
The following experiment was planned to secure data on this 
point. Soil from plot 113 of the Leon station was used: 
Pot 161 and 162 check. 
Pot 163 and 164 manured. 
Pot 165 and 166 sterilized. 
Pot 167-168 manured and sterilized. 
Manure leachings were used for treatment. 3 inch flower pots 
were used because four of them would go under the available bell 
jars. 165-166-167-168 after being filled were wrapped in paper 
and put in the autoclave and kept for 45 minutes at 10 pounds 
pressure. 4 Petri dishes were also sterilized. These were for the 
pots to set in. The inside of the bell jar was washed out with a 
saturated solution of mercuric chloride and a glass plate was also 
washed off with this disinfectant. Red clover seed was put in 
a small E flask and washed with a saturated solution of mercuric 
chloride and then well rinsed with sterile water three times. About 
fifteen of these sterile seeds were planted in each pot by means of 
a flamed forceps. The surface was scratched and the seeds cov- 
ered about one-fourth inch deep. The pots were watered with 
sterile water and the four sterilized pots covered with a large bell 
jar, and the four unsterilized pots covered with another bell jar, 
so that conditions would be parallel. The planting was done Octo- 
ber 23d. By November 7th it was seen that sterilization was not 
complete, for the four pots which were supposed to be sterile had 
mold on the surface and the plants were looking sickly. The clover 
on the unsterilized pots was looking fairly well, but growing very 
slender. By November 27th the clover on the sterilized pots was 
all dead, evidently killed by the mold. On the unsterilized pots the 
clover had made a fair growth. A count of the bacteria and mold 
on the sterilized pots was made at this time by inoculating some 
agar plates by the usual method. The idea was simply to see if 
the soil was sterile, and not to know just how many bacteria or 
molds were present. 
