188 ' OF MANURE. 



grain, the roots, and the stem, and now proceed to 

 the consideration of the most important object of 

 agriculture, viz. the production of nitrogen in a form 

 capable of assimilation, — the production, therefore, 

 of substances containing this element. The leaves, 

 which nourish the woody matter, the roots, from 

 which the leaves are formed, and which prepare the 

 substances for entering into the composition of the 

 fruit, and, in short, every part of the organism of a 

 plant, contain azotized matter in very varying pro- 

 portions, but the seeds and roots are always partic- 

 ularly rich in them. 



Let us now examine in what manner the greatest 

 possible production of substances containing nitro- 

 gen can be effected. Nature, by means of the atmo- 

 sphere, furnishes nitrogen to a plant in quantity suffi- 

 cient for its normal growth. Now its growth must 

 be considered as normal, when it produces a single 

 seed capable of reproducing the same plant in the 

 following year. Such a normal condition would suf- 

 fice for the existence of plants, and prevent their 

 extinction, but they do not exist for themselves 

 alone ; the greater number of animals depend on the 

 vegetable world for food, and by a wise adjustment 

 of nature, plants have the remarkable power of con- 

 verting, to a certain degree, all the nitrogen offered 

 to them into nutriment for animals. 



We may furnish a plant with carbonic acid, and all 

 the materials which it may require ; we may supply 

 it with humus in the most abundant quantity ; but it 

 will not attain complete development unless nitrogen 

 is also afforded to it ; a herb will be formed, but no 

 grain ; even sugar and starch may be produced but 

 no gluten. 



But when we give a plant nitrogen in considera- 

 ble quantity, we enable it to attract with greater en- 

 ergy from the atmosphere the carbon which is neces- 

 sary for its nutrition, when that in the soil is not 

 sufficient ; we afford to it a means of fixing the car- 

 bon of the atmosphere in its organism. 



