88 KANSAS ACADEMY OF SCIENCE. 
In 1890 Mr. S. R. Boyce, my assistant, made a distillation of a large quantity 
of the ground root. He obtained by this process an oil of a yellowish color, which 
soon blackened. This oil has a very acrid taste and pungent odor, evidently con- 
taining the medical properties of the root in concentrated form. 
ROOT TUBERCLES ,AND THEIR PRODUCTION BY INOCULATION. 
BY D. H. OTIS, MANHATTAN. 
Read before the Academy October 28, 1897. 
HISTORY AND LITERATURE. 
GENERAL STATEMENT.— By examining the roots of such plants as clover, al- 
falfa, beans, and peas, one will usually find, scattered over their exterior surface, 
tubercles of various sizes and shapes. These tubercles are, with very few excep- 
tions, peculiar to a certain order of plants known as Leguminose, and, as far as 
agricultural plants are concerned, only to the suborder Papilionacee. These 
tubercles are the outgrowths of the plants themselves, and are produced by the 
action of certain micro-organisms working within the tissues of the root. For- 
merly, these tubercles were considered abnormal appendages and as injurious to 
the plants; but later observations revealed the fact that, where these tubercles 
were wanting, the plants did not make the growth that was made by plants 
where the tubercles were present. Later examination has brought out the fact. 
that these tubercles are the homes of minute microscopic bacteria, Bacillus 
radicicola Beyer. The bacteria have the remarkable property of taking the 
free nitrogen of the atmosphere and transforming it into available compounds 
for plant food. So it isa case of symbiosis, the plant furnishing food and shelter 
for the bacteria, and the bacteria in turn furnishing the plant with nitrogen. 
This is what makes the leguminous plants so valuable as soil enrichers, and es- 
pecially prized for green manuring. 
Earty Opinions CONCERNING THE TUBERCLES.—It is just about a century 
ago that root tubercles became the subject of agricultural inquiry and experi- 
mentation. The early ideas were very crude, some supposing the tubercles to be 
fungi, others lenticels, root branches, swellings caused by insects, and some used 
them as a part of the description of plants. Even those who took them to be 
peculiar to the order Leguminos entertained widely different views as to their 
functions. Some thought they were swollen lateral roots used in the absorption 
of food, or, still better, a storehouse for reserved food material. Others main- 
tained that they were dwarfed roots, while still others classed them as imperfect 
buds, capable of developing into new plants. About fifty-five years ago Boussin- 
gault carried on a series of experiments with a large number of plants, from 
which he concluded that not even the leguminous plants had the power to obtain 
free nitrogen from the air. Similar experiments at Rothamsted confirmed 
Boussingault’s conclusions. It should be noted, however, that these experiments 
were conducted under the conditions of sterilization and enclosure which elimi- 
nated the micro-organisms from the soil. Thus it will be seen that the earliest 
conclusions were very incomplete, and in many cases were the result of mere su- 
perficial observation. 
Investigation of the structural and etiological phase of the subject was begun 
in 1816. It was started by Woronin, and he was followed by Eriksson, DeVries, 
Schindler, Cornu, Mattei, Kny, Prillieux, and, in 1879, by B. Frank. It was 
about this time that M. Berthelot called in question the accuracy of the conclu- 
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