106 Balls . — Apparent Fallacies of 
was slightly over 200 mm. The inertia of the moving coil in this instru- 
ment is fairly high, so that it is not easy to decide what the real 
momentary values of the response might be. Since the experiments were 
all strictly comparative this is unimportant. An ordinary ‘ good response ’ 
gave about 40-50 mm. deflexion. 
Three methods of stimulation were used in the preliminary work, 
namely, mechanical injury, induction shocks through independent electrodes 
applied over one or the other non-polarizing electrodes, and induction 
shocks through the latter themselves with the galvanometer out of circuit. 
In the latter method, which was the only one employed regularly, a falling 
key broke the primary and then closed the galvanometer circuit in rapid 
succession. 
The non-polarizable electrodes were of the U-tube pattern, mounted in 
pairs with an interval of 15 mm. between the centres of their contacts with 
the tissues. It was found that all trouble from their polarization was best 
avoided by dismounting them after an hour’s work and cleaning them ; the 
zincs were dipped in weak sulphuric acid and washed in running water, the 
glass plugs removed, cleaned and washed, and stuffed afresh with filter 
paper and a cap of clay, all wetted with o-6 per cent, saline. After the 
electrodes had been used for four or five hours, fresh saturated zinc sulphate 
was placed in the U -tubes. 
Experimental Results. 
Feebleness of response from the root.— The first disappointment of these 
trials was the weak response obtained from young roots of about a milli- 
metre in diameter, however the electrodes were placed. Old woody roots 
responded freely. 
Since it seemed likely that the effect of a break shock through the 
electrodes might be less effective than a local stimulation over one electrode, 
such stimulation was tried, but with no better results. A notable blow from 
a falling lever was required to produce a slight response, and in no case — 
either with roots or other tissues — was it found possible to obtain a larger 
response by any other method than the simple one of a break shock 
through the electrodes. 
Response dependent on structure . — It seemed then that the magnitude 
of the response was in part due to the non- homogeneity or anisotropy of 
the length of tissue tested. Thus, with one electrode on the hypocotyl and 
the other on the root, large responses were usually obtained, and next in 
magnitude to these were the responses from the last two internodes of the 
main axis, where one electrode was on semi-meristematic tissue and the 
other on partly differentiated tissue (Table I). The direction of the initial 
response with moderate shocks was a function of the structure ; thus, with 
