ACORNS 79 



The Electrical Structure of the Radicle. 



We have seen that the radicle and the plumule are covered 

 with a cuticle — that of the former being especially tough — 

 and I have little doubt that these are insulating processes, 

 similar to the sheaths of medullated nerves or the sarco- 

 lemma of voluntary muscular fibre. 



Now the earth gives out negative current and we know 

 that the roots, stem and venation of every tree and plant 

 growing in the earth are negatively charged. 



If the thick cuticle which covers the radicle provided 

 e£Eective insulation from the earth the charge communicated 

 to the root would, of necessity, be an induced one and would 

 therefore be of positive sign. As that does not obtain the 

 charge must be direct, and there is no want of evidence 

 that it is so. 



Careful examination will reveal the fact that some, if 

 not all of the lower root filaments are bare of this cuticle 

 at their tips, which are white instead of the brown of the 

 radicle itself. In the very young seedlings, before root 

 filaments are formed, the tip of the radicle itself is bare 

 and in that way current is picked up, or at all events it is 

 in that way that the circuit is completed. 



When the skin is stripped from the plumule the latter 

 presents a smooth, even appearance but the radicle exhibits 

 fibres which connect electrically with the root filaments. 

 There is indeed a resemblance to 

 the junction of animal nerve-fibres 

 with the sarcomeres of voluntary 

 muscle. Calling the cuticle the 

 sarcolemma, the root filaments pene- 

 trate it and join up with the root 

 fibres. The root filaments, in fact, 

 convey current through an insulating 

 process to certain conductors inside 

 the radicle. ""^"^ ff'g.JJ 



The above sketch is of a portion of the plumule and radicle. 



