314 'Researches on Vegetation. 



maintenance more or less proper for retaining heat and 

 moisture : these authors have supposed that the vital force, 

 both animal and vegetable, might, by decomposing or com- 

 bining in different ways atmospheric air and water, produce 

 all the substances, and even the salts, cartlk^, and metals, 

 which are proved, by analysis and incineration, to exist in 

 vearetables. This confused idea is not more susceptible of 

 being proved than that of making gold from substances 

 which contain none of it. Before we have recourse to un- 

 intelligible transmutations, miraculous, and in opposition 

 to all tlie observations known, we ought to ascertain exactly 

 that plants do not acquire and find these principles ready 

 formed in the mediums in which they expand." 



This part of the work contains a great number of new 

 observations and happy comparisons between experiments 

 and agricultural observations ; but 1 shall confine myself to 

 general results. 



Roots and plants absorb salts and extracts, but in a less 

 proportion than water which holds these salts and extracts 

 in solution. 



The salts which the roots have absorbed are found in 

 plants without any change in their state of nature. 



It is to be w^ishcd that the author would extend his re- 

 searches on the formation of the acids which seem to be the 

 product of vegetation ; such as the oxalic acid, the citric, 

 and the tartarous. 



A vegetable does not absorb in the same proportion all 

 the substances contained at the same time in the same so- 

 lution ; it forms particular secretions of them : thus, in a 

 solution of different salts the roots take up more of one kind 

 than of another ; in general they absorb in greater (quantity 

 the substances the solutions of which, when separated, are 

 less viscous. 



When we compare the weight of extract which can be 

 furnished by the most fertile soil with the weight of the dry 

 plant which has expanded in it, it is found that it could 

 have derived from it but a very small part of its substance. 



Saussure proceeds to examine the ashes w hich vegetables 

 leave by combustion, lie proves that all the predominating 

 principles in ashes are contained in the vegetable mould, 

 and that its soluble part, which alone penetrates into the 

 vegetable, contains these principles in a greater proportion 

 than the Insoluble part: their existence in the plant, then, 

 has nothing natural, as he observes, and their absence in 

 it would excite more astonishment. 



Plant?, 



