MECHANICAL RESPONSE TO STIMULUS 



21 



by attaching the leaf to the long arm of the recording Optic 

 Lever, and shortening the distance of the recording surface. 

 The records given in figs. 15 and 16 were automatically 

 obtained by the impression of 

 the moving spot of light on a 

 sensitive film wrapped about 

 the recording drum. The leaf 

 was excited by a single strong 

 induction-shock. In order to 

 obtain the complete curve of 

 response and recovery — the 

 double process being accom- 

 plished in the course of about 

 seven minutes— the first record 

 was taken on a slowly moving 

 drum. For the detailed study of the characteristic time- 

 relations of the first part of the curve, again, two more 

 records were obtained, one with a moderate (fig. 15) and the 



Fig. 15. Photographic Record of 

 Response and Recovery of Mimosa, 

 taken on a slowly moving drum. 

 Record shows actual movement 

 reduced to one-third. 



Fig. 16. Photographic Record of Response in different specimen, taken 

 on a faster-moving drum showing only first part of the curve. Each 

 division of time-scale = -5 second. 



other with a rapid speed of drum (fig. no). The last of 

 these enables us to obtain time-measurements which are 

 accurate to less than -^ of a second. The method by 



