8 ELECTRICAL STRUCTURE AND 



Everything, therefore, that grows in the earth is charged 

 by the earth through the roots, and by the air through the 

 flowers and leaves (the lungs, as it were, of the tree or 

 plant), so that in the roots, stem, stalks, and veins the 

 tree, shrub, or plant has its negative terminals, while those 

 parts of the leaves between the veins are positive. 



Examination of the vascular bundles and laticiferous 

 vessels of plants will make this clear. 



In all fruits and vegetables the negative and positive 

 systems are plainly discernible once the eye has been 

 taught to look for and recognise them. 



Before going into detail, however, it will be as well to 

 consider the electrodes. 



I found that when two wires of equal gauge and length, 

 soldered to two steel needles of exactly the same gauge and 

 length, were connected to the terminals of the galvanometer 

 and the needles were inserted in various objects and 

 liquids, certain deflections were observed, and that such 

 deflections were not momentary but constant. 



These deflections are explained as being due to galvanic 

 action. 



There are two theories, i.e. 



(1) Two metals that is to say, one needle being 

 electrically positive to the other in one exciting 

 liquid, or 

 . (2) One metal in two such liquids. 



It will, however, be only necessary to consider the first 

 seriously. 



Let us suppose that we are using two wires of exactly 

 equal length soldered to two steel needles as before men- 

 tioned, and that the object under examination is an apple. 

 In order to settle which is the positive and which the 

 negative side of the galvanometer scale from its central 

 zero, we will first connect the positive or carbon terminal of 

 a dry cell to the right-hand terminal, and the negative or 



