ii8 RESEARCHES ON IRRITABILITY OF PLANTS 



15*2 spaces between stimulus and initiation of response. 

 The latent period of the specimen is therefore '076 of a 

 second. 



I have been able, moreover, to construct a vibrating- 

 recorder whose frequency is 500 times per second, a fact 

 which enables an easy determination of time-intervals of 

 less than a thousandth of a second to be made. These 

 recorders, owing to their excessive lightness, possess the 

 additional advantage of having a very small moment of 

 inertia. It is obvious, therefore, that the employment of 

 such recorders not only bears favourable comparison with 

 those at present used in animal physiology, but would also 



Fig. 70. — The previous record magnified. 



have the advantage of reducing the error due to inertia 

 to the lowest possible minimum, and of making the record 

 itself its own chronogram. 



It has been said that owing to the extreme lightness 

 of the vibrating-recorder, the shght error usually due to 

 instrumental inertia is here negligible. To what extent 

 this is true may be judged by taking records from the same 

 leaf with two separate recorders of different sizes and 

 comparing the results. If the factors of inertia were promi- 

 nent, then two such determinations of an identical latent 

 period would give results varying somewhat from each 

 other. I therefore took two different records from the 



