Bacteriological Studies of the Fixation oe Nitrogen. 
21 
time in 1910 when I took my sample Oct. 25. The soil is a clay loam 
with considerable gravel, in good condition, and so far as I could ob¬ 
serve there was no brown color visible although this had been reported 
as occurring earlier in the season. The land sloped well so there should 
be ample opportunity for drainage. When introduced into mannite 
solution, an infusion of this soil produced a heavy, wrinkled surface 
membrane, with scattering brown patches, the growth being almost ex¬ 
clusively Azotobacter. The increase in nitrogen in this culture was 
14.7105 m. g. in thirty days. 
Sample No. 27. 
The material for the next study was obtained from an orchard 
where evidence of nitre was observed for the first time in the summer 
of 1910. This was an old orchard and a number of the largest trees 
were very badly injured but not yet dead. There was no indication of 
the trouble other than the firing of the green leaves. In an adjacent 
orchard, there had been heavy loss the previous year and all signs point¬ 
ed to a repetition of the disaster for 1910. The soil was a heavy clay 
and my sample consisted of the surface two inches taken between two 
of the affected trees. The culture obtained from the soil infusion of 
this soil yielded a heavy, wrinkled, surface membrane with isolated 
brown patches. The increase in nitrogen in the culture in thirty 
days amounted to 11.3481 m. g. 
Sample No. 28. 
The next sample was taken from what had been a young orchard 
three years previously. It had been given the best of care which may 
have hastened the appearance of the destroying agents. The tract con¬ 
tained approximately twenty acres sloping gently to the south and west. 
Some years before it was set to orchard, a reservoir had been built 
on the northeast corner, the highest point on the place. This was not a 
success since it was producing a seeped condition in the lower sur¬ 
rounding country and it had to be abandoned. This was about four 
years before the orchard was planted. The soil is a clayey loam, 
for the most part, underlaid with a shale. In 1908 the mealy nature 
of the surface was first observed. At this time Dr. Headden took a 
sample and states that the conditions did not afford an opportunity 
for him to judge the color. I have visited this orchard two differ¬ 
ent times since then and it has so happened each time I have been there 
that the soil either has been so extremely dry that no color was vis¬ 
ible or else it had just been cultivated and all traces on the irrigating 
furrows had: been obliterated. Four acres of the young orchard died 
in the spring of 1909 and by fall the area involved had nearly doubled. 
In Oct., 1910, there were scarcely three acres of the original twenty 
alive. The living trees were all to be found in the five or six rows 
along the highest side of the tract. When the first injury appeared 
in 1909, we learned that this same four acres had given trouble in 
former years, when the land was in alfalfa, so it was to be expected 
