CONSTITUENTS OF PLANTS. 99 



always as a double acid salt, on whatever soil they 

 may grow. The potash in grapes, also, is more fre- 

 quently found as an acid salt, viz. cream of tartar, 

 than in the form of a neutral compound. As these 

 acids and bases are never absent from plants, and 

 as even the form in which they present themselves 

 is not subject to change, it may be affirmed, that 

 they exercise an important influence on the deve- 

 lopment of the fruits and seeds, and also on many 

 other functions of the nature of which we are at 

 present ignorant. 



The quantity of alkaline bases existing in a plant 

 also depends evidently on this circumstance of their 

 existing only in the form of acid salts, for the capa- 

 city of saturation of an acid is constant ; and when 

 we see oxalate of lime in the lichens occupying the 

 place of woody fibre, which is absent, we must regard 

 it as certain, that the soluble organic salts are des- 

 tined to fulfil equally important, though different 

 functions, so much so, that we could not conceive 

 the complete development of a plant without their 

 presence, that is, without the presence of their 

 acids, and consequently of their bases. 



From these considerations we must perceive that 

 exact and trustworthy examinations of the ashes of 

 plants of the same kind growing upon different 

 soils would be of the greatest importance to vege- 

 table physiology, and would decide whether the 

 facts above-mentioned are the results of an un- 

 changing law for each family of plants, and whether 



H 2 



