PROPERTIES OF THE LEAF OF DIOMA. 
39 
Leaf fresh 
1. Excitation of the same side 
2. „ ,, opposite side . 
After repeated excitation :— 
3. Excitation of the same side . . 
4. „ „ opposite side. 
Later :— 
5. Excitation of the same side . 
6. „ ,, opposite side. 
Still later :— 
7. Excitation of the same side . 
8. ,, „ opposite side . 
0-15" 
0*26 // 
0*50' 
0'84" 
0-53" 
0-78" 
1*54" 
3-50" 
These Kew experiments showed that at the ordinary temperature of summer the 
interval of time between excitation and response is considerable, and that its length 
depends on the distance of the seat of excitation from the led off surfaces, and is much 
longer in injured leaves than in fresh ones. But for reasons which I have already 
stated in discussing the fundamental experiment, it is certain that time measurements 
made by the method of signalling are incapable of giving an answer to the question 
of the rate at which the excitatory effect is propagated. During the hot weather of 
last summer (July, 1881) we had the opportunity of making experiments with the 
pendulum rheotome which proved in the clearest way that, under favourable con¬ 
ditions, the rate of propagation in the leaf of Dionsea is extremely rapid. 
From the extreme difficulty which was met with last summer in obtaining plants in 
vigorous condition, I was prevented from making as many observations as I deemed 
desirable. Of those which were made I think it best to submit the results of one only, 
which was perfectly satisfactory :— 
Period of closure. 
Same lobe 
excited. 
Opposite lobe 
excited. 
0-02 ,/ to 0*04"* 
0 
0 
0’02 // „ 0'06" 
-11 
0 
0'02 ,/ „ 0-08" 
-22 
0 
0*02" „ 0*10" 
-31 
0 
0-02" „ 0T25" 
• • 
9 
0-02" „ 0T5" 
■ • 
26 
0T0" „ 0-20" 
• • 
50 
In this experiment the plant was placed in the chamber at 38° C. and remained at 
that temperature throughout. The leaf was led off as in the fundamental experiment. 
The excitation was by induction shocks. The exciting electrodes were applied on the 
* Trace at 0’05'. 
