INVARIABLE QUANTITY OF ALKALINE BASES. 109 



be considered with the strictest attention both by 

 the agriculturist and physiologist. 



We have no reason to believe that a plant in a 

 condition of free and unimpeded growth produces 

 more of its peculiar acids than it requires for its 

 own existence; hence, a plant, on whatever soil it 

 grows, must contain an invariable quantity of alka- 

 line bases. Culture alone will be able to cause a 

 deviation. 



In order to understand this subject clearly, it will 

 be necessary to bear in mind that any one of the 

 alkaline bases may be substituted for another, the 

 action of all being the same. Our conclusion is 

 therefore by no means endangered by the existence 

 of a particular alkali in one plant, which may be 

 absent in others of the same species. If this in- 

 ference be correct, the absent alkali or earth must 

 be supplied by one similar in its mode of action, or 

 in other words, by an equivalent of another base. 

 The number of equivalents of these various bases 

 which may be combined with a certain portion of 

 acid m\ist necessarily be the same, and therefore the 

 amount of oxygen contained in them must remain 

 unchanged under all circumstances and on whatever 

 soil they grow. 



Of course, this argument refers only to those 

 alkaline bases which in the form of organic salts 

 form constituents of the plants. Now, these salts 

 are preserved in the ashes of plants as carbonates, 

 the quantity of which can be easily ascertained. 



It has been distinctly shown, by the analysis of 

 De Saussure and Berthier, that the nature of a soil 

 exercises a decided influence on the quantity of the 

 different metallic oxides contained in the plants 

 which grow on it ; that magnesia, for example, was 

 contained in the ashes of a pine-tree grown at Mont 

 Breven, whilst it was absent from the ashes of a 

 tree of the same species from Mont La Salle, and 

 that even the proportion of lime and potash was 

 very different. 



10 



