there is an equally important question not concerned in 

 this process, namely the source for nitrogen. Nitrogen is 

 of course an essential element for the construction of pro- 

 toplasm. As is well known most plants can utilize it in 

 simple combination with oxygen in the form of a nitrate, 

 a sharp contrast, by the way, to the typical animal which 

 requires it offered as an organic compound. It is also 

 known that the same plants cannot assimilate the free 

 nitrogen of the atmosphere, and further, in the processes 

 of decay, free nitrogen is liberated by the breaking 

 down of the nitrogen compounds in dead organic matter. 

 The logical conclusion of these momentous facts is that 

 soon all the world's supply of combined nitrogen would 

 be exhausted, neglecting the relatively small replenish- 

 ment induced by cosmic forces so .that green plants and 

 consequently animals, would not have the wherewithal to 

 live, unless there were some organisms which could avail 

 themselves directly of this inert gas. Now there are 

 plant organisms which have the ability to assimilate the 

 uncombined nitrogen of the air, certain bacterial forms, 

 and it also appears some somewhat higher plants. But the 

 operations that lead to this result are by no means satis- 

 factorily explained, and the whole topic is one of live 

 interest both from a theoretical as well as a practical stand- 

 point. It should be added that from the latter point of 

 view, a process by which a combination of nitrogen with 

 other elements in a form that is acceptable to green plants 

 has been devised, and bids fair to become of great import- 

 ance, for combined nitrogen is the great need of the organic 

 world. 



The processes of nitrification naturally lead us to the 

 question of the elaboration of nitrogen compounds with- 

 in the cell, of the final construction of proteid material 

 that is the actual food of the protoplasm ; but here we are 

 much in the dark, partly because we have so little real 



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