12 



PLANT RESPONSE 



obtain the curve of recovery. 1 If we apply similar stimuli 

 successively, we obtain successive responses which are alike 

 (fig. 7). But if stronger stimulus be applied, by means of 

 stronger heating current, the amplitude of response will be 

 correspondingly increased. 



In the simple instance which we have considered, the 

 response-record was obtained by taking advantage of the 

 sudden contraction of the india- 

 rubber. In the response of con- 

 tractile animal muscle, we obtain 

 response-records in exactly the 

 same manner (fig. 8), and such 

 records are known as myographs 



(fig. 9). 



Similar contraction in length, or 

 LONGITUDINAL RESPONSE under 

 the action of stimulus, has been 

 shown byl Pfeffer to occur in the 



Fig. 8. 



Mechanical Lever 

 Recorder 



Fh;. 7. Response of India-rubber 



Thermal stimulus for i second at 

 intervals of two minutes. 



The muscle M with the attached 

 bone is securely held at one 

 end, the other end being con- 

 nected with the writing lever. 

 Under the action of stimulus 

 the contracting muscle pulls 

 the lever, and moves the 

 tracing point to the right 

 over the travelling recording 

 surface r. When the muscle 

 recovers from contraction the 

 tracing point returns to its 

 original position. See on P 

 the record of muscle-curve. 



filament of the sensitive stamens of Cynerece. I shall, how- 

 ever, show in Chapter IV. that such longitudinal contraction 

 under stimulus is not unique, but a phenomenon very exten- 

 sively exhibited by plant-tissues, as seen in the series of 

 uniform responses to stimulation, obtained from the stamen 

 of an ordinary plant, which is here given (fig. 10). 



1 Such models made of catgut and stretched caoutchouc have been used by 

 Engelmann for explaining muscle response. 



