ELECTRIC PULSATION IN DESMODIUM GYRANS. 409 
Electric Response-curve. 
I selected specimens where the movement of the leaflet took 
place gradually, without jerks, and where the up-and-down 
movement was approximately in a straight line. On taking 
a record of electric response, I was surprised to find that, 
corresponding to each complete mechanical vibration, there 
is produced a double electric pulsation—a large principal wave 
(a), followed by a smaller subsidiary wave (0). Such double 
response, mimicking the dichrotic pulse-record of the heart-beat, 
I have found in all the specimens I have tried. In the case 
whose record is given (fig. 2), the period of complete mechanical 
vibration was about 3°5 minutes. The period of the principal 
electrical wave of response was slightly less than one minute, 
that of the subsidiary wave was slightly over 2°5 minutes. 
These double electric pulses, corresponding to a single mechani- 
cal vibration, are at first very puzzling, and 1 undertook special 
investigations to clear up this obscure point. In the concluding 
part of this paper I shall adduce experimental results which will 
satisfactorily explain the peculiarity. 
The Sign and Intensity of Electric Response. 
As regards the sign of response, I have shown (Journ. Linn. 
Soc., Bot. xxxv. (1902) p. 277) that in ordinary plants and 
under normal conditions the current of response flows, in 
the plant, from the more to the less excited portion of the 
tissue. This is generally the case also in the electric response 
in animal tissue. In Desmodium gyrans I have found it so 
in all cases hitherto examined; that is to say, the current of 
response in the plant flows from the excitable petiolule A to 
the resting petiole B (fig. 1). 
I may, however, mention here certain conditions which mght 
give rise to a reversed response. I have shown that when a 
plant is in a depressed vital condition, the direction of current 
of response is apt to be reversed. Again, the response under 
feeble stimulation may be abnormal or reversed, but under 
stronger stimulation it may become normal again*. Curiously 
enough, I have obtained similarly opposed responses, to feeble 
aud strong stimuli respectively, with inorganic substances—in 
metals under mechanical stimulus and under the stimulus of 
* Bose, ‘Response in the Living and Non-Living ’ (Messrs. Longmans). 
