114 BOARD OF AGRICULTURE. 



invite your particular attention : First, that nitrogen occurs 

 in two distinct conditions in nature, namely, as free uncom- 

 bined nitrogen, or in combination with other elements ; and, 

 secondJi/, it is an indispensable constituent of every organ of 

 plants and animals. 



Accepting these statements as focts, we ask quite naturally 

 as next in order. In what relation does the nitrogen stand in 

 its various natural forms to organic life in general? Do the 

 free nitrogen and the combined nitrogen — as ammonia, or 

 nitric acid — or the more complex forms of organic nitrogenous 

 substances, act aliivc beneficially on groAving plants? Thanks 

 to the labors of De Saussure, Liebig, Boussingault, and others, 

 our answers to these questions are to-day quite concise. De 

 Saussure was the first investi2:ator who assumed the indifier- 

 ence of the atmospheric free nitrogen towards plants. Liebig 

 supported subsequently his assumption by theoretical argu- 

 ments, and Boussingault proved it by experiment as correct. 



Professor Ville's observations, which seemed to contradict 

 Boussingault's results, have lost their importance since Law's, 

 Gilbert's and Piigh's careful series of experiments have been 

 published. It is therefore at present generally conceded that 

 plants cannot directly assimilate the free nitrogen of the air, 

 but have to supply their wants from already existing nitrogen 

 combinations. 



Ammonia and nitric acid are recognized in consequence of 

 experimental demonstration as the principal forms of nitrogen, 

 which the vegetable organisms can convert into plant-food ; 

 whilst the more complicated organic nitrogen compounds, 

 so called nitrogenous substances, are known to serve directly 

 as plant-food only in the earliest stage of the young plants, 

 during the formation of the first leaves, and also in the case 

 of parasitic plants. For all other purposes in the vegetable 

 econom}^ they have to undergo a total disintegration, and 

 their nitrogen has to be changed into nitric acid or annnonia, 

 according to circumstances, before it is fit for assimilation by 

 leaves and roots. Considering, then, the question settled, re- 

 garding the only form in which the nitrogen can serve as 

 plant-food, it becomes of interest to study the natural resour- 

 ces of nitrogen convertible into phuit-food, with reference to 

 their availability for the successful cultivation of farm crops. 



