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dried, and containing 1.733 grams of nitrogen. The total fixation 
of nitrogen amounted to 1.715 grams for the surface of the flowerpot, 
or 274 kilograms per hectare. 
It is a remarkable fact that before the formation of the fruit. the 
nitrogen in the Leguminose is, by preference, localized in their roots. 
This fact is due to the great richness of the tubercles with which they 
are covered. Bréal found in the nodules of several plants, such as 
kidney beans, peas, lupins, lentils, acacia, etc., as much as 7 parts 
of nitrogen to a hundred of dried material, even when the fibers of 
the roots never contained more than 2.5. 
Another fact, not less interesting, brought to hght at the same time 
by the experiments of Hellriegel and Wilfarth, is the difference 
shown by arable soils in their capacity to initiate the appearance of 
tubercles upon the roots of leguminous plants. Some of them are 
very efficient in this respect; others are much less so. There are even 
some soils which are more favorable to the production of tubercles 
in certain species of plants*than in others. This is a fact very diffi- 
cult of explanation, for the solution of which further and bacteriolog- 
ical researches will be necessary, because variations of this kind can 
only be due to a difference in the microbe itself, the penetration of 
which into the roots produces these nodules. 
In the experiments of Hellriegel and Wilfarth the sowings were 
made with the washings from ear Sane containing, as we know, a mul- 
titude of micro-organisms having different functions. Some of them, 
it is true, were made with a liquid containing a little of the white 
substance which comes from the nodules when they are crushed, but 
all precautions had not been made to get rid of the germs which the 
water itself might have contained, or w hich might have been brought 
either by the young plant or by the atmospneric dusts. 
It was therefore necessary in order to be sure that the fixation of 
the nitrogen was really due solely to the bacteria of the nodule to 
repeat the preceding experiments with all the precautions required 
by microbic researches. 
This work of revision was carried out with scientific rigor by 
Prazmoffski, in Cracow, with great success. 
The vessels used for growing the plants were provided with a 
cover, which fitted tightly and had four holes pierced in it. One of 
these holes, made in the center, permitted the young plant to pass 
through it. The three others allowed of watering and of the pas- 
sage of a current of pure air. All these holes were closed with plugs 
made of a sterile wadding, which prevented the entrance of all germs 
of exterior organisms. 
The soil was formed of about 3,500 grams of siliceous sand, pre- 
viously washed in boiling hydrochloric acid, then in water, and 
finally heated red hot. Pure mineral fertilizers without any nitro- 
gen whatever were then added to it. 
The whole mass was then sterilized by being heated for at least 
two hours from 140° to 150° C. 
In these vessels peas which had been previously sterilized were 
sown. To effect this they were first plunged into a solution of cor- 
rosive sublimate, then washed in alcohol, which latter was finally 
set on fire and burned upon the seed itself. 
Some of the vessels received also bacteroidal germs contained 
in a nonnitrogenized bouillon culture liquid. 
