might have been expected a lively discussion
sprung up over the conflicting results of Boussin
gault and Ville, and Dr. Pugh associated himself
with Messrs. Lawes & Gilbert for the purpose of
reinvestigating the subject, and, if possible, of
reaching decisive results.
It is, .of course, foreign to the purpose of this
paper to describe his investigation in detail, in
cluding as it did, besides the main question, many
experiments upon various collateral points. The
main features of the investigation, however, are
readily comprehended. He grew plants in a soil
freed from all compounds of nitrogen by ignition
and washing, and confined them in an atmosphere
also deprived of all nitrogen compounds ; the
plants. being supplied with all other necessary
foods, if they had the power to assimilate the free
nitrogen of the air, they should have grown, and a
comparison of the amount of nitrogen in the plants
with that in the seed would show how much had
been assimilated.
The results of the investigation were entirely
negative; no assimilation of nitrogen being ob
served, either by gramiriaceous or leguminous
plants. This investigation was a model of careful
and accurate experimenting in every detail, and
was for a long time believed to have settled the
question. It is, therefore, a striking illustration
of the difficulty of reaching absolute truth about
nature processes, as well as of the need for caution
in drawing conclusions from experimental results,
that while the more recent investigations have not
in the least degree• impugned the accuracy of Dr.
Pugh's work, they have nevertheless practically
reversed his conclusion.
Another interesting fact is that many practical
students of agriculture refused to accept these
negative results and insisted that leguminous crops
did in some way assimilate nitrogen from the air
and thus serve to enrich the soil in that element,
and for a long time there was a sort of subdued
but irrepressible conflict between the teachings of
scientific investigation and the results of practical
observation.' About iBBi, a more acute stage of
THE FREE LANCE.
the discussion was percipitated by the publication
of results obtained by Schulz, a German. Schulz's
estate of Lupitz possessed by nature a very poor
sandy soil. By manuring with potash compounds
and growing leguminous crops, chiefly lupines,
Schulz was able to vastly increase its fertility. In
his publications, he attributes this increased fer
tility to the assimilation of atmospheric nitrogen
by the leguminous crops. A very lively discussion
followed the publication of these results and var
ious hypotheses were advanced to bring the results
into harmony with the supposed teachings of
science. Curiously enough, just about the time
this discussion subsided, experimental results began
to be published which differed radically from those
cf Boussingault and of Lawes, Gilbert & Pugh, in
that they showed a very considerable assimilation
of free nitrogen. Among the earliest of these re
stilts were those obtained by Prof. W. 0. Atwater,
at the Weslyan University in Conn., with peas, by
the method of sand culture. Since then, the sub
stantially concordant results of Hellriegel & Wil
farth, Wolff, Breal, Lawes & Gilbert, Frank, Praz
mowtki and others have established the fact that
leguminous plants grown under suitable conditions
do acquire large amounts of nitrogen from the air,
either directly or indirectly.
As was before stated, this conclusion does not
in the least impugn the accuracy of Dr. Pugh's
experimental work. The key to the apparent dis
crepancy between the results of earlier and later
investigation lies in the words "suitable condi
tions." These later investigations have shown
that the assimilation of free atmospheric nitrogen•
by leguminous plants is intimately connected with
the formation of the so-called root tubercles, and,
furthermore, that these root tubercles are the re
sult of the action upon the plant of certain bac
teria which enter into a very curious and interest
ing symbosis with the plants.
It has been shown that leguminous plants grown
in sterilized soil, that is to say, in soil in which all
organisms have been destroyed by heat, do not
form tubercles and do not assimilate free nitrogen,