184 
IOWA ACADEMY OF SCIENCE 
February 16th the wheat series was replanted for the third time. 
The soil was not resterilized. The seed was sterilized by immersion 
for ten minutes in 5% formalin and then rinsed in sterile water. * 
This time the seed grew, or enough of them grew so that a com- 
parison could be made. All pots both sterilized and unsterilized 
were covered with bell jars so that conditions would be identical. 
All plants grew well up till the first of March, when 406, the ster- 
ilized check began to fail. In a few days 405, its duplicate began 
to show signs of dying. By March 6th, 408 was turned decidedly 
yellow and the tips of the leaves were dried up. 
On March 8th a sample was taken from each pot to determine 
the number of bacteria in each. Each sample was secured by tak- 
ing a small amount on the end of a flamed spatula from three dif- 
ferent places just below the surface on each pot. This was placed 
in sterile Petri dishes, thoroughly mixed and about one-fourth 
gram taken from each and placed in sterile test tubes for dilution. 
Two agar plates were poured from each with dilutions of 100 and 
1,000 respectively. No effort was made to get exact numbers, but 
the notes made were as follows : 
401. Many bacteria, many species, colonies all sizes, one mold. 
402. Many bacteria, many species, colonies all sizes, one mold. 
403. Ten times as many bacteria as 401, colonies the same, twenty molds. 
404. Twenty times as many bacteria as 401, colonies the same, twenty molds. 
405. Many bacteria, colonies mostly very small. Few large ones. 
406. One-tenth as many bacteria as 401, colonies mostly very small. 
407. Bacteria very numerous, colonies all quite small. 
408. Bacteria very numerous, colonies all quite small. 
It is seen that none of the pots were sterile, but it is plainly seen 
that the character of the flora has been changed by the sterilization. 
It would seem that one species which has the characteristic of form- 
ing very small colonies on agar plates survived the sterilization in 
all four pots and that in addition, pots 405 and 406 became later 
inoculated with other bacteria. There were no molds on the 
sterilized pots. On March 9th the poorest one of each of the 
duplicates was harvested and the data is here given: 
Pot 
No. of 
Plants 
Green 
Wt. g. 
Wt. per 
Plant 
Relative 
Weight 
40JL 
2 
.240 
.120 
100 
404 
3 
1.265 
.422 
351 
406 
3 
.445 
.148 
123 
408 
3 
1.275 
.425 
354 
