108 OF THE INORGANIC CONSTITUENTS OF PLANTS. 



potash, soda, lime, or magnesia. These bases evi- 

 dently regulate the formation of the acids, for the 

 diminution of the one is followed by a decrease of 

 the other : thus in the grape, for example, the quan- 

 tity of potash contained in its juice is less when 

 it is ripe than when unripe ; and the acids, under 

 the same circumstances, are found to vary in a simi- 

 lar manner. Such constituents exist in small quan- 

 tity in those parts of a plant in which the process 

 of assimilation is most active, as in the mass of 

 woody fibre ; and their quantity is greater in those 

 organs whose office it is to prepare substances con- 

 veyed to them for assimilation by other parts. The 

 leaves contain more inorganic matters than the 

 branches, and the branches more than the stem. 

 The potato plant contains more potash before blos- 

 soming than after it. 



The acids found in the different families of plants 

 are of various kinds ; it cannot be supposed that 

 their presence and peculiarities are the result of 

 accident. The fumaric and oxalic acids in the liver- 

 wort, the kinovic acid in the China nova, the ro- 

 cellic acid in the Rocella tinctoria, the tartaric acid 

 in grapes, and the numerous other organic acids, 

 must serve some end in vegetable life. But if these 

 acids constantly exist in vegetables, and are neces- 

 sary to their life, which is incontestable, it is equally 

 certain that some alkaline base is also indispensable, 

 in order to enter into combination with the acids 

 which are always found in the state of salts. All 

 plants yield by incineration ashes containing car- 

 bonic acid ; all therefore must contain salts of an 

 organic acid.* 



Now, as we know the capacity of saturation of 

 organic acids to be unchanging, it follows that the 

 quantity of the bases united with them cannot vary, 

 and for this reason the latter substances ought to 



* Salts of organic acids yield carbonates on incineration, if they 

 contain either alkaline or earthy bases. 



