IOWA ACADEMY OF SCIENCE 
185 
It is here seen that sterilization helped the growth of the wheat 
on the untreated soils, and did not hinder it any on the manured 
soil. The plants on all the pots were thrifty, except 406. The 
plants on it were nearly dead. 
The cause of the trouble with the wheat on pots 405 and 406, 
the untreated sterilized pots, was given consideration. It was 
thought that it might be due to lack of nitrates in these pots; as 
nitrification could not go on in a sterile soil, possibly the nitrates 
were all used up and the plants were consequently dying. To test 
this hypothesis the following experiment was planned: The pots 
from which the plants had just been cut, were elevated on a ring 
stand, distilled water was applied to the surface until it percolated 
through, this dropped on to a filter and from this was caught in a 
graduate. This filtrate was tested for nitrates with the brown ring 
test. The percolates from all the pots showed the presence of 
nitrates very decidedly. The percolate from 406 was tested the 
second time and each time it gave a distinct test for nitrate. Pot 
408 gave a very strong test for nitrates. So it is evident that 
the plants in pot 406 were not dying for lack of nitrates. 
March 16th the remaining pots were harvested and the data is 
given below. The plants on 403 and 407 were very thrifty, those 
on 402 were one-third dead and those on 405 were one-fourth 
dead, and the whole plant looking yellow and sickly. 
Pot 
Treatment 
No. 
Plants 
Green 
Wt. g. 
Wt. per 
Plant g. 
Relative 
Weight 
402 
0 
2 
.552 
.276 
100 
403 
Man. 
4 
2.988 
.747 
270 
405 
Ster. 
5 
1.600 
.320 
116 
407 
Man. Ster. 
4 
3.150 
.787 
285 
It is seen here also that sterilization has helped the growth of 
the wheat, whether the soil is manured or not. The fact that ster- 
ilization was not complete, but only partial, destroys much of the 
force of this argument, but still it is felt that there was some 
sterilization and that some of the species of bacteria were elim- 
inated and that this data has some value. 
It was decided to test the reaction of the soil to see if the species 
which formed the small colonies, made the soil acid. To do this, 
soil extract was obtained as before, 100 cc. portions were placed in 
a beaker, brought to a boil to expel C0 2 and titrated with N-50 
acid and alkali solutions, lacmoid being used as an indicator. None 
