412 PROF. Je C. BOSE ON THE 
say, the electric response undergoes gradual diminution from 
a maximum to a minimum, after which it again attains the 
maximum value and repeats the cycle. In the record given 
(fig. 4) the electric response gradually declined to a minimum 
at the third set of double responses, after which it attained the 
first maximum value, only to repeat the cycle. 
In connection with this it is interesting to note that 1 
obtained exactly similar periodic fatigue with ordinary plants 
in responses to uniform mechanical stimuli. In the record 
Fig. 5, 
Periodic fatigue exhibited by a specimen of petiole of Cauliflower. ‘The responses 
are to successive uniform mechanical stimuli applied at intervals of one 
minute. 
given in fig. 5, alternate responses exhibit fatigue. In other 
cases, I found the cycle completed after the third or fourth 
response. 
Interference Effects. 
It will be understood from what has been said before, that 
the direction of the responsive current in the plant, and the 
consequent direction of the galvanometric deflection, depend on 
the relative quiescence or excitability of the two contacts. If, 
of the two contacts (see fig. 1), B be quiescent and A excited, 
the current of response in the plant will be from A to B; the 
galvanometer connection being properly adjusted, this will give 
rise to an upward or, say, positive deflection. The petiolule 
being periodically excited, there would be produced a periodic 
(double) electric pulsation, whose sign would be positive. 
In Desmodium there are two lateral leaflets, and both of 
them, usually speaking, execute periodic movements. If now 
one of the contacts be shifted from the resting-point B in 
the main petiole to the petiolule A’, we shall get extremely 
interesting interference effects. 
1. Suppose both the leaflets execute periodic movements, 
and suppose the mechanical oscillations of both are in the 
