Bacteriological Studies of the Fixation of Nitrogen. 13 
My sample was secured in September, 1909, and in thirty days gave 
a fixation of 3.57265 m. g. of nitrogen. In culture it produced a lemon 
yellow membrane on the surface with a similar growth in the bottom 
of the flask. There was a slight acid production accompanied by a 
butyric, cheesy odor. 
Fig. 2. Nitre spot in a sugar beet field. Sample No. 6. 
Samples Nos. 7 and 8. 
These samples were taken from a deserted field where the brown 
areas had become very numerous and extensive. The Russian thistles 
which had been the last inhabitants of these spots had died and left 
them bare. Adjoining orchards were suffering from the nitrate 
burning. The trouble was first noticed here in 1908 and in Septem¬ 
ber of 1909 I took my two samples. No. 6 came from a brown spot, 
five feet in diameter and No. 7 was taken three feet outside this affect¬ 
ed area. In both cases the surface two inches were discarded and the 
next four inches collected. The soil was a red, gypsiferous clay and 
no water occurred anywhere near the surface. In culture, these two 
resembled each other very closely. They produced a yellow membran¬ 
ous growth, with some gas, little acid, and a cheesy odor. No. 7 de¬ 
veloped a more typical Azotobacter membrane than No. 8. This was 
composed largely of the characteristic Azotobacter forms and numer¬ 
ous other small rods and clostridia, but no brown color developed. 
The membrane produced by No. 8 was not as heavy as No. 7, but was 
made up of practically the same forms. In thirty days soil No. 7 
fixed 3.01215 m. g. and No. 8, 2.87205 m. g. of nitrogen. 
Sample No. 9. 
All of the samples which had been collected thus far had been from 
either high nitre spots or immediately adjoining areas, and it seemed 
