FUNCTION IN PLANT LIFE 25 



as the lymph space on a nerve-fibre or the copper taping on 

 an insulated wire in preventing an induced charge from 

 passing it. 



Now the part a, a is positively charged by the air and 

 has greater surface area than the conducting layer c. 

 We should therefore find as we do find that the tension 

 of c is in excess of that of a, a, and that the sign is negative 

 instead of positive. 



That is while the seed is still attached to the tree and 

 has no separate and independent existence. 



But in course of time the pod falls and releases the seed 

 by splitting segmentally. The latter we must suppose to 

 be planted or buried in the soil and to be thereafter depen- 

 dent upon the earth, as man is mainly dependent upon the 

 air as the source of electrical energy. Obviously, then, 

 some change must take place to enable the seed to survive, 

 and that change is a very important one. The conducting 

 layer, c, dries up, and therefore ceases to intercept charge, 

 but the outer membrane, d, after contact with the damp 

 soil, would become a conductor, and without the inner 

 membrane, b, no electrical system could obtain. But with 

 d as a conductor and b as the insulating material, induction 

 could take place, and the seed substance receive a positive 

 induced charge in the following manner 



\ charge 



Jffembrane 01,. conductor 



6, : non-conductor 

 ?eed 5ufofan.ce : conductor 



Fig. 24. 



so that the two membranes are necessary both while the 

 seed is in the pod and after it has been released. 



Fig. 25 shows the final appearance of the membranes 



