9 



CHAPTER II. 



ACCOUNT OF THE THEORIES ON THE ABSORPTION 

 OF NITROGEN FROM THE AIR BY THE LEGU- 

 MINOS/E. 



Chief Researches. 



The function of fixation of atmospheric nitrogen by 

 plants is a problem which not only is of interest to scientists 

 under the head of plant physiology, but which also has its 

 primary application in the fertilization of the soil, and it is 

 particularly from this double point of view that it is of 

 interest to agriculturists. From the day when observant 

 minds were eager to understand the eflfect of crops on the 

 soil which had borne them — which is looking back thousands 

 of years, seeing we have to deal with agricultural scientists 

 like Columella — it was noted that the soil seemed im- 

 proved after a crop of leguminous plants, such as lupin, 

 vetch, &c., and we may say that all work undertaken on 

 the subject of fixation of atmospheric nitrogen has its origin 

 in these observations, since the^' were made in order to 

 understand the reason for the soil, after having produced 

 the leguminous plants supplying a considerable amount of 

 nitrogenous materials in the shape of fodder and seed, being 

 found subsequently just as rich, if not richer, in this element, 

 considered as being the most potent in plant growth. 



However, at the start, which represents an epoch now 

 fairly remote, seeing that authentic research only began with 

 Boussingault in 1838, attention was chiefly paid to consider- 

 ing whether plants actually did absorb nitrogen from the 

 air. At this period this faculty was not only assigned to 

 the Leguminosse, but to all plants, and Boussingault himself 



