SUBSTITUTION OF ALKALINE BASES. 113 



of oxygen which each species of plant contains in 

 the bases united with organic acids. In all proba- 

 bility such inquiries will lead to most important 

 results ; for it is clear that if the production of a 

 certain unchanging quantity of an organic acid is 

 required by the peculiar nature of the organs of a 

 plant, and is necessary to its existence, then potash 

 or lime must be taken up by it in order to form salts 

 with this acid ; that if these do not exist in suffi- 

 cient quantity in the soil, other bases must supply 

 their place ; and that the progress of a plant must 

 be wholly arrested when none are present. 



Seeds of the Salsola Kali, when sown in common 

 garden soil, produce a plant containing both potash 

 and soda ; while the plants grown from the seeds of 

 this contain only salts of potash, with mere traces 

 of muriate of soda. (Cadet.) 



The examples cited above, in which the quantity 

 of oxygen contained in the bases was shown to be 

 the same, lead us to the legitimate conclusion, that 

 the development of certain plants is not retarded 

 by the substitution of the bases contained in them. 

 But it was by no means inferred that any one base 

 could replace all the others, which are found in a 

 plant in its normal condition. On the contrary, it 

 is known that certain bases are indispensable for the 

 growth of a plant, and these could not be substituted 

 without injuring its development. Our inference has 

 been drawn from certain plants, which can bear 

 without injury this substitution ; and it can only be 

 extended to those plants which are in the same con- 

 dition. It will be shown afterwards that corn or 

 vines can only thrive on soils containing potash, and 

 that this alkali is perfectly indispensable to their 

 growth. Experiments have not been sufficiently 

 multiplied so as to enable us to point out in what 

 plants potash or soda may be replaced by lime or 

 magnesia ; we are only warranted in affirming that 

 such substitutions are in many cases common. The 

 ashes of various kinds of plants contain very diflFer- 



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