PLANT RESPONSE 41 
photographic record of fatigue in the leaf-stalk of 
cauliflower. 
It is evident that residual strain, other things being 
equal, will be greater if the stimuli have 
been excessive. This is well seen in 
fig. 23, where the set of first three 
curves Ais for stimulus intensity of 45° 
vibration, and the second set B, with an . 
augmented response, for stimulus in- 

tensity of 90° vibration. On reverting 
1 7 os 6 ro Fic. 22. — Faticur 
in € to stimulus intensity of 45°, the Ee Ee 
responses are seen to have under- _ CX™7EOWEE 
Stimulus: 30° vibration 
gone a great diminution as compared ®t, intervals of one 
F c minute. 
with the first set a. Here is seen 
marked fatigue, the result of overstrain from excessive 
stimulation. 
If this fatigue be really due to residual strain effect, 
then, as strain disappears with time, we may expect the 
390° 
+> 45° 
os 

A B ( D 
Fie. 23.—Errect oF OvEeRsTRAIN IN Propucine FaticuE 
Successive stimuli applied at intervals of one minute. The intensity of 
stimulus in C is the same as that of A, but response is feebler owing to 
previous over-stimulation. Fatigue is to a great extent removed after 
fifteen minutes’ rest, and the responses in D are stronger than those in C. 
The vertical line between arrows represents ‘05 volt. (Turnip leaf-stalk.) 
responses to regain their former height after a period 
of rest. In order to verify this, therefore, I renewed the 
stimulation (at intensity 45°) after fifteen minutes. It 
