PIIESENT STATE OF ORGANIC ELECTRICITY. 313 



a passage of descending jnices), cither with the most central 

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

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

 tending from these layers to the neighbouring organs." 



It would appear, therefore, that currents pass from the 

 contiguous surfaces of the hark and wood f)f the dicotyle- 

 donous plant outwards towards the cuticle, and inwards to 

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

 which excite currents in the opposite dii-ections through the 

 galvanometer wire. 



Currents in tlic Hoot and its Dependencies. — According to 

 ]M. Wart man n,* in some roots the centi-al 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 Becquerel t has found the central 

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

 in relation to the exterior. 



In the potato, in the tubers of the Helianthus tuhcrosus 

 and Lathyrus tulcrosus, 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 tubere of Tropdolum tuberosian, and Ullucus 

 tubcrosus, the currents are reversed, and cniTcspond, there- 

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

 dicotyledonous stem. 



* J)if>. Univ. dr Oi'nUrt; toiu. xv. 



t Jleiiioirc sur les eirets i-ltrtri<|ues obU'nus dans Ics tuWrcules, Ics racines, 

 "etles fruits, au uioycu d'aiguilleii Je plutiac."— i/«rt. (Ul'AcmL dts Scunces, 

 torn, xxiii. 



