16 ELECTRICAL STRUCTURE AND 



not appear to be provided with so efficient a repair outfit. 

 In common with the potato, it has a marginal negative 

 system and several positive terminals, but I should imagine, 

 from the number of root-filaments, that instead of being 

 dependent upon the mother -plant it derives its electrical 

 supply directly from the earth. 



LEAVES. 



I selected a few examples from evergreen and deciduous 

 leaves with a view to seeing what difference, if any, 

 existed between them as regards relative conductivity, the 

 ramifications of their negative systems, and the quality of 

 the main conductors the stalks through which current 

 is conveyed to them from the earth. 



As a rule, in deciduous leaves the veins do not seem to 

 me to form so complete and extensive a network as in 

 those of the evergreen variety. They are, moreover, not 

 so well insulated, are thinner in texture, and, if they lose 

 their moisture under the influence of prolonged summer 

 heat, become electrically inert and fall. Such a leaf is 

 that of the horse-chestnut (Fig. 18), and it offers a sharp 

 contrast to that of the ivy (Fig. 19), in which the negative 

 veins form an almost complete network, and which carries 

 three principal veins as against the single one of the horse- 

 chestnut. The leaf is also more substantial, is infinitely 

 better adapted to retain its moisture, and therefore its 

 conductivity and capacity of electrical absorption, while 

 the walls of the veins appear to possess high resistance, 

 or, in other words, a high degree of insulation ; the inter- 

 mediate or positive parts of the leaf being able in the 

 presence of occasional rain or even a damp atmosphere to 

 receive positive charge from the air. 



This perfection of insulation and inherent interior 

 moisture extend to the stems of the plant, so that, their 



