104 OF THE INORGANIC 



by means of the direct and positive observations 

 referred to, which have shown that plants have the 

 power of returning to the soil all substances unne- 

 cessary to their existence ; and the conclusion to 

 which all the foregoing facts lead us, when their 

 real value and bearing are apprehended, is that the 

 alkaline bases existing in the ashes of plants must 

 be necessary to their growth, since if this were not 

 the case they would not be retained. 



The perfect development of a plant according to 

 this view is dependent on the presence of alkalies 

 or alkaline earths ; for when these substances are 

 totally wanting, its growth will be arrested, and 

 when they are only deficient, it must be impeded. 



In order to apply these remarks, let us compare 

 two kinds of tree, the wood of which contain un- 

 equal quantities of alkaline bases, and we shall find 

 that one of these grows luxuriantly in several soils, 

 upon which the others are scarcely able to vegetate. 

 For example, 10,000 parts of oak wood yield 250 

 parts of ashes, the same quantity of fir-wood only 

 83, of linden-wood 500, of rye 440, and of the herb 

 of the potato-plant 1500 parts*. 



Firs and pines find a sufficient quantity of alkalies 

 in granitic and barren sandy soils, in which oaks 

 will not grow ; and wheat thrives in soils favourable 

 for the linden-tree, because the bases, which are 

 necessary to bring it to complete maturity, exist 

 there in sufficient quantity. The accuracy of these 

 conclusions, so highly important to agriculture and 



* Berthier, Annales de Chimie ct cle Physique, t. xxx. p. 248. 



