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relation in which each organism gains advantage. So far as the 
bacteria are concerned, they doubtless gain a place for developing 
a breeding pouch, and perhaps gain some sustenance from the 
root of the pea. So far as the pea plant is concerned, the presence 
of the organism makes possible the assimilation of free nitrogen. 
In all of the experiments which have been carried on it has been 
found that the production of the tubercles is necessary to enable 
the legumes to assimilate nitrogen. Where the legumes develop 
without tabercles on account of the lack of bacteria in the soil, no 
nitrogen was assimilated, and where the tubercles were very abund- 
ant, much nitrogen was taken from the air. It is plain then that 
the pea plant obtains a considerable advantage from its association 
with the lower organism. 
As to the method by means of which this association of organ- 
isms extracts the free nitrogen from the air, we are as yet in the dark. 
That it is free nitrogen that is assimilated by the plant and not 
combined nitrogen, has been demonstrated by the experiments of 
the last two years, but where the nitrogen is first fixed is as yet a 
question. It has been suggested that the bacteria themselves 
take the nitrogen out of the air and store it up in these tubercles; it 
has been suggested that the bacteria stimulate the legumes in such 
a way as to enable the legume to seize the free nitrogen from the 
air and store it in the roots; and it has been suggested that the 
assimilation of the nitrogen is a matter of the combined action of 
the bacteria and the legume life together. Which of these possibil- 
ities is the proper one science has not yet indicated, but it has 
been satisfactorily proved that through the combined life of the bac- 
teria in the root of the pea plant nitrogen is taken from the air and 
stored up in the roots of the pea plant in the form of nitrogen 
compounds of high complexity. che 
The work on this subject of nitrogen assimilation at the outset 
seemed to indicate that the family of legumes alone possess the 
power of absorbing nitrogen from the air. Undoubtedly, this fam- 
ily possesses this power to a greater extent than any other family 
of plants, but it is still a question whether the same power is not 
developed in certain other plants. Upon this matter experiment- 
ers are not in agreement at the present time, for while some ex- 
periments have plainly pointed to a nitrogen assimilation of non 
