Electrical Response in Cotton Plants. 105 
Bearing in mind that the experiments were undertaken simply in 
order to develop a Testing Method rather than as a real investigation of 
these phenomena in themselves, the following data may possibly be of use 
for the reference of other plant physiologists who also have been sceptical 
as to these apparently lawless outbreaks of energy. 
Apparatus . — The home-made apparatus employed was based on that 
described by Waller, with modifications. Its only notable feature was 
a mercury switchboard, arranged in such a way that two pairs of electrodes 
— the tested object and a control — were always handled alternately (Fig.). 
By bridging over from cup to cup, it was possible to obtain in a very few 
minutes the resistance of the tissues and a series of antidrome and homo- 
drome responses from both alternately, with occasional observations of the 
circuit zeros, of the galvanometer zero, and of the deflexion of either circuit 
by a standard voltage. 
Another set of bridges on the same board enabled a Method of Balance 
to be employed whereby the control and the test-object were connected 
in series and then in parallel, and stimulated with a single shock from the 
inductorium ; if the two were identical, no response resulted from stimulation 
in parallel, and any fatigue effects were equally shared by both, while an 
increased fatigue on the part of one over the other led to an increase in 
the compound response with each successive stimulation. Since there are 
numerous risks of manipulation in this method — which I believe is original 
— it was used as a supplement to the simple alternate testing. 
A few trials were made on plants in sitii in the field along a telegraph 
wire, but the difficulty of avoiding electrode fallacies makes this method 
impracticable, and it was only tried in order to make sure that the response 
of an organ was much the same before and after its removal from the 
plant. 
Resistances were measured by a Post Office box with a Paul Unipivot 
galvanometer. Induction shocks — always breaks — were given by a small 
Ruhmkorff coil, purchased locally, whose description I am unable to give ; 
with one Leclanche cell it gave a spark about one-fiftieth of a millimetre 
long, which was the usual stimulus, as being strong enough to induce marked 
fatigue after four or five repetitions ; tetanization with this stimulus was 
bearable by wetted fingers on the electrode zincs. 
The galvanometer employed was the Ayrton-Mather, made by the 
Cambridge Scientific Instrument Co., with a resistance of 22 ohms at 
I 5 ° C., giving a deflexion of 155 mm. for one microvolt at a distance of 
one metre. This instrument is by no means an ideal one for the purpose, 
being somewhat insensitive, but this fact does not vitiate the particular 
results obtained, since the method employed was a comparative one 
throughout, as described above. 
The maximum ‘ response ’ deflexion obtained in some 2,000 stimulations 
