SOURCE OF THE NITROGEN. 165 



obtain this additional supply of nitrogen, but from the nitric 

 acid 1 Nitrate of potash produced a similar effect. It is 

 well known what a powerful effect salts of nitric acid, espe- 

 cially salt-petre or nitre, have upon the growth of vegetables. 

 This influence must be due to the nitrogen which is fur- 

 nished to the gluten, vegetable albumen, and other products 

 of the vital power. 



Upon the whole, then, it is highly probable, that plants de- 

 rive their nitrogen from ammonia, crenic, apocrenic and ni- 

 tric acids, and that vegetation will be abundant in proportion 

 as these substances are supplied to the roots of plants. They 

 are not, however, introduced in their pure state, but are com- 

 bined with inorganic bases, in the form of salts, and are de- 

 composed, and their elements assimilated by chemical and 

 vital forces.* 



But whatever theories we may form on this subject, upon 

 the source and assimilation of the carbon, hydrogen, oxygen 

 and nitrogen of plants, one thing is certain, that the farmer 

 must supply vegetable and animal manures which contain 

 these elements, or the carbonic acid, water and ammonia of 

 the atmosphere, will not be gathered into the form of vegeta- 

 ble productions. The necessity of supplying the soil with 

 manure, cannot be set aside, by any theories of the source 

 from which plants derive their support ; and the best theory 

 is that which shall best explain the facts, and point out the 

 most direct and efficient means for increasing the quantity 

 and quality of the productions of the farm. And we believe 

 it will be found in the end, that plants derive their carbon, hy- 

 drogen, oxygen and nitrogen from the several sources named, 

 and that they are endowed with the power of adapting them- 

 selves to circumstances, so as to select a greater or less quan- 

 tity from each source ; but that one alone will not support 



* Since writing the above, I have received two works, Johnson's 

 Lectures, and Dana's Muck Manual, which substantiate the views 

 given in the text. 



14* 



