FUNCTION IN PLANT LIFE 28 



same law which governs cell -division should guard the 

 immature seed from the possibility of premature germina- 

 tion by withholding from it a perfected electrical system. 

 Unless that is so there is a flaw in our reasoning, or our 

 understanding of the law is at fault. 



THE HORSE-CHESTNUT. 



At the time of year of the experiments about to be 

 described (September) and for the following few weeks 

 the seeds were in various stages of development, and could 

 be studied at leisure. The method adopted was to 

 cut the pods in halves longitudinally and test them gal- 

 vanometrically, to ascertain the relative sign and electrical 

 activity of their various parts. The following photo- 

 graphs are illustrative of the result : 



Outer Lnsu[at<nfme m 6rane 



Fig. 22. SECTION OF HORSE-CHESTNUT. [Original photo.] 



a, a, part, consisting of white, pithy substance, which is positively 

 charged ; b, insulating membrane immediately enveloping the seed 

 substance ; c, conducting layer, negatively charged ; d, insulating mem- 

 brane enveloping the conducting layer ; e, seed substance yielding only a 

 few millimetres positive deflection as against the 1,000 mm. negative of 

 the conducting layer ; /, outer insulation, porous, and of low resistance. 



The next photograph shows the negative terminal and 

 system more clearly, and gives a better idea of the extent 

 of the positively charged material. This seed is not in 



