40 RESEARCHES ON IRRITABILITY OF PLANTS 



interval the plate has moved a certain distance. There 

 is a second key used for short-circuiting by which the clock 

 interrupter can be put out of action. When this is done, we 

 obtain the usual series of dots at intervals of 'i second. 

 It will be understood that if the whole response-record 

 were to be made by the vibrator, as actuated periodically at 

 intervals of 10 seconds, we should have a very long gap in the. 



Fig. 13. — Clockwork for the dot-marker; the six-rayed wheel 

 periodically completes electric circuit. 



record of the contraction-portion, since the apex is reached 

 in 2 seconds. To obtain then a more or less continuous 

 inscription of the entire curve, the vibrator should at first 

 be allowed to make its normal dots *i second apart. This is 

 done by taking care to commence the experiment with the 

 clock-interrupter short-circuited. As soon as the apex point 

 is reached the short-circuit is removed, and the succeeding 

 record, during the recovery of the leaf, consists of dots 



