10 THEORIES ON THE ABSORPTION OF NITROGEN 



carried out his researcties on the Gramineie as well as on 

 the Leguminosae. 



Priestley and Theodore de Saussure were the tirst to 

 employ scientific methods in order to demonstrate this 

 absorption. In fact, Priestley, in his work " Experiences 

 and Observations of Different Kinds of Air," relates how 

 he placed a plant of Epilobium hirsutuni in a vessel lo in. 

 high bv I in. wide, which at the end of a month had 

 absorbed seven-eighths of the available nitrogen. 



Ingenhoutz, in his " Experiences sur les Vegetaux, " 

 affirms that all plants have the power of absorbing nitrogen 

 gas. 



Theodore de Saussure gives an account, in his " Re- 

 cherches chimiques sur la Vegetation," of the experiments 

 he made with plants placed either in atmospheric air or in 

 pure nitrogen, and from which he draws a negative con- 

 clusion ; that is to say, he denies the faculty of plants for 

 absorbing nitrogen from the air. 



Theodore de Saussure gives his conclusions thus : " If 

 nitrogen is a simple body, if it is not an element of water, 

 one must be forced to recognize that plants are only able 

 to assimilate it in the form of plant and animal extracts and 

 ammonia vapours, or other compounds soluble in water, 

 which they are able to absorb from the soil and from the 

 atmosphere." 



Woodhouse and Senebier came to the same conclusion. 

 Sir Humphry Davy (1812) brought no new contribution 

 to the subject of the fixation of atmospheric nitrogen, but 

 greatly encouraged through his work the application of 

 science to agriculture. 



In 1838, Boussingault, remarking that crops made use 

 of nitrogen, and that the soil fertility was maintained with- 

 out the addition of nitrogenous manures, was of the opinion 

 that the greater part of this nitrogen must of necessity come 

 from the atmosphere. 



With the object of checking the likelihood of this 



