SOURCES OF NITROGEN. 159 



1. The atmosphere contains seventy-nine parts of nitro- 

 gen in one hundred, and as it is thus brought into direct con- 

 tact with the organs of plants, either as a gas, or dissolved in 

 water, it must be absorbed. Hence some have supposed it 

 possible, that a part of that found in vegetable bodies is de- 

 rived from that source.* But the nitrogen of the air possesses 

 such inert and indifferent properties, as to render it nearly cer- 

 tain, that it is not assimilated directly ; although we cannot 

 say what the vital power may effect. It is probable, however, 

 that nitrogen enters plants in some of its combinations. The 

 question whether it came originally from the atmosphere, is 

 quite different from the one now under consideration — the 

 immediate source of it. 



2. Ammonia, as we have seen p. 81, is produced in consid- 

 erable abundance. It must be brought into contact with the 

 leaves and roots of plants, and enter into their organs. It is 

 composed of fourteen parts of nitrogen and three of hydrogen. 

 That plants derive a part of their nitrogen from it, appears 

 exceedingly probable from the following considerations. 



(1) Ammonia is found in the sap of trees, and in the juices 

 of all vegetables. *' The products of the distillation of flowers, 

 herbs and roots, with water, and all extracts of plants made 

 for medicinal purposes, contain ammonia. Ammonia exists 

 in every part of plants, in the roots (as in beet-root), in the 

 stem of the maple-tree, and in all blossoms and fruit in an 

 unripe condition."! In these cases ammonia may possibly 

 be formed by the living power, or it may be the effete matter 

 arising from transformations ; but that such is the fact is ex- 

 tremely doubtful. 



(2) That ammonia yields nitrogen to plants, is highly pro- 

 bable from the action of animal manures. Gluten is a sub- 

 stance containing the largest quantity of nitrogen in wheat, rye 

 and barley, and is found in different proportions. The more ani- 

 mal manure there is employed in the cultivation of these grains, 



* Johnson. t Liebig. 



