LIFE OF FLANTS. 



345 



The wonderful combination of primary matters, and the changes 

 which are produced in ingredients derived from the soil and 

 from water, can only be explained by this influence of the gal- 

 vanic power, and it is in the same manner that we daily per- 

 ceive more distinctly that wherever heat assists in the solution 

 of bodies, electricity is produced, as in every chemical process 

 the electrical relations are changed. Art has already imitated, 

 by means of the voltaic pile, many of these operations of na- 

 ture, by proving that carbon, colouring matters, alkalies, and 

 earths, are but oxides of metals, which distinctly resume 

 their metallic nature at the negative pole of the voltaic pile. 

 Finally, even in the operation of impregnation, there is unde- 

 niably an electrical or galvanic process, which is evolved by 

 the elementary contraction of opposite substances, as ancient 

 observers of the physiology of vegetables had observed. 



374. 



Oxygen is one of the most important and common stimu^ 

 lants in the vegetable world. We have already (314. 329.), 

 seen that plants attract oxygen, and it is certain, that in the 

 germination of seeds the influence of this body is of consider- 

 able importance. It has, indeed, been long known, that 

 salts, lime, and weak acids, powerfully promote germina- 

 tion, — that seeds, which have long been laid by, are forced to 

 unfold themselves by hydrochlorous acid, — and even that an 

 excessive excitiement is produced by too powerful an applica- 

 tion of these salts and acids. For experiments have made it 

 obvious to sight, that plants, treated with these acids, spring 

 up speedily indeed, but on account of their too speedy and 

 active growth, are destitute of any proper power of increase, 

 ' and that they hence easily decay without bearing fruit. This 

 experiment, which has been confirmed by Lampadius in 

 particular, shews, that oxygen is not properly a nourishing 

 substance, nor becomes assimilated to the plant, but that it 

 only increases thg vital activity in the capacity of a stimulus ; 

 (Hermstadt's Archiv der Agricultur-Chemie). This, also, 

 is further evident from other experiments, in which we see 

 that almost as much oxygen is either exhaled or employed in 

 the composition of the carbonic acid which is exhaled, ha4 



