Bacteriological Studies of the Fixation of Nitrogen. 19 
nitrates, which had proven disastrous to the trees, had also had its 
detrimental effect upon the nitrogen fixing flora. 
Sample No. 21. 
This sample, a red sandy loam, was taken in an orchard, July 1910, 
where the conditions were much the same as those described for No. 20. 
The orchard included about two acres along one side of which ran 
a twenty foot wash so that every chance for good drainage was afford¬ 
ed. The trees had begun dying here in 1910 and were about all gone 
by late summer. The soil was brown along the ditch banks and irri¬ 
gating furrows. I11 culture a moderately heavy, white film, contain¬ 
ing Azotobacter, formed on the surface of the medium and there was 
some butyric fermentation. The increase in nitrogen after thirty days 
amounted to 2.8014 m. g. 
Sample No. 22. 
In this sample we have one of the most severe cases of nitrate 
destruction which we have ever recorded. Here is a 90 acre orchard 
which showed the first symptoms in 1908, and today at least forty-five 
acres are entirely dead or will be by fall. The soil varies from a red 
clay to a sandy loam and there is no water at five feet. When sampled 
late in July, 1910, scattering trees were badly affected, but many were 
showing only a few burned leaves on the water sprouts. The irrigat¬ 
ing furrows showed a light brown stain, more especially on the crests 
than along the sides, since the orchard had been irrigated recently and 
it was rather difficult to distinguish the brown color from the moist 
conditions of the furrow. There was little doubt at this time that the 
trees were in a very dangerous condition but it was hardly expected 
that in less than a year half of the tract with its fifteen year old apple 
trees would be waste land. This soil gave a heavy white gelatinous 
membrane composed mostly of Azotobacter cells and after thirty days 
the nitrogen of the culture had increased 8.89635 m. g. 
Sample No. 23. 
We come next to an orchard where the soil is a red clay loam. 
1 his is one of the more recent orchards to show the burning and 
nothing unusual was observed here until July, 1910. At this time very 
few of the trees were killed outright but many were in the first stages 
and some were in a very critical condition The area of the 
orchard was about forty acres and over one half of the trees are dead 
today. The soil showed almost no brown color when I took my sample, 
due possibly to the peculiar red color naturally present. I am in¬ 
clined to believe that at this time the nitrates had not become extreme¬ 
ly high or more of the trees would have been killed and we should 
undoubtedly have seen more of the brown stain. The culture from 
this sample showed almost no surface growth but a white membrane 
on the bottom and sides of the flask. Along with this there developed 
a marked foecal odor. Azotobacter was present in quantity. The in¬ 
crease in nitrogen in thirty days due to fixation amounted to 7.14^1 
