Conductivity wider Geotropic Stimulation. 



353 



the thread, which was waxed over for insulation. Two blocks of paraffin 

 wax, K, K, were fixed to the cork near the base, and to each a brass binding 



Fig. 5. 



screw, I', was fixed by means of wire staples, which were sunk in the wax, 

 but did not penetrate to the cork. Two terminals, L, L, consisting of thin 

 platinum wires fixed to small strips of zinc, were then attached to the 

 binding screws. Connection with the induction coil and the metre bridge 

 was made with insulated wires fixed in the binding screws. To the side of 

 G was fixed a large pin 'bent so that it formed an indicator on the scale, 

 0, and by resting on the plug, P, kept the whole in position. The bean, after 

 the root-tip had been coated with wax, was fixed with two pins to the sheet 

 cork, so that the root was parallel to the surface of the cork^ and to the 

 vertical thread, S. The wires were then inserted on the " front " of the root, 

 M, with all due precautions. After the plug of wax had been placed in 

 position to keep the wires from moving, the unwaxed portion of the plant 

 was covered with wet lint to keep it moist. 



By tilting G and fixing it in position by means of the indicator pin and the 

 plug P, the root could be placed so that the wires were in either the upper 

 or the lower side. In the records of the experiments given below + angles 

 were taken as those where the wires were in the physically upper side of the 

 root and - angles as those in which they were in the physically lower side. 



