PRESENT STATE OF ORGANIC ELECTRICITY. 313 



a passage of descending juices), either with the most central 

 parts (the pith or the perfect wood), or with the parts more 

 exterior (the young bark), a lateral current will be found 

 tending from these layers to the neighbouring organs." 



It would appear, therefore, that currents pass from the 

 contiguous surfaces of the bark and wood of the dicotyle- 

 donous plant outwards towards the cuticle, and inwards to 

 the pith ; or at least, arrangements exist in these directions 

 which excite currents in the opposite directions through the 

 galvanometer wire. 



Currents in the Eoot and its Dependencies. According to 

 M. Wartmann,* in some roots the central structures and the 

 cortical structures are, as in the stem, positive in relation to 

 the layers by which they touch and are united. 



Centrifugal transverse currents would appear to exist in 

 certain roots, which resemble tubers in the quantity of their 

 nutritious deposits. For Becquerelf has found the central 

 part of the carrot, and of the red and white beetroot, negative 

 in relation to the exterior. 



In the potato, in the tubers of the HeliantJius tuberosus 

 and Lafhyrus tulerosus, currents radiate from the centre to 

 the cuticle ; for the electrode at the centre is negative in 

 relation to the other, the latter indicating a more positive 

 condition the nearer it is placed to the cuticle. Becquerel, 

 who has ascertained these facts, and refers them to the system 

 of transverse currents in the bark, states at the same time 

 that in the tubers of Tropceolum tuberosum, and Ullucus 

 tuberosus, the currents are reversed, and correspond, there- 

 fore, with the transverse system in the wood and pith of the 

 dicotyledonous stem. 



* Bib. Univ. de Geneve, torn. xv. 



t Memoire sur les effets electriques obtenus dans les tubercules, les racines, 

 " etles fruits, an moyen d'aiguilles de platine." Mem. de I'Acad. des Sciences, 

 torn, xxiii. 



