88 CHAP. X. EFFECT OF MECHANICAL STIMULATION 



at the beginning (fig. 42). The growth-rate is greatly 

 depressed under intense stimulation, and the period of 

 recovery then becomes very much protracted, 



I have often been puzzled by the fact that specimens 

 apparently vigorous exhibited little or no growth after 

 attachment to the Crescograph. After waiting in vain 

 for an hour, I had to discard them for others with equally 



Fig. 42, 



Fig. 43. 



Fig. 42. Effect of mechanical friction on growth. 

 N, normal rate ; f, retarded rate immediately after friction ; 

 A, partial recovery after 15 minutes. Successive dots at 

 intervals of 5 seconds (Zephyranthes). 



Fig. 43. Effect of pin-prick on growth. 



N, normal rate ; w, immediate effect after wound ; a, partial 



recovery after an hour (Zephyra,nthes). 



unsatisfactory results. One of these specimens happened 

 to be left attached to the recorder overnight, and I was 

 greatly surprised to find that the specimen which had shown 

 no growth the previous evening, now exhibited vigorous 

 growth after being left to itself for 12 hours. I then reahsed 

 that the temporary arrest of growth had been due to stimu- 

 lation caused by the somewhat rough handling during 

 the process of mounting and attachment of the specimen 

 to the recorder. 



The prolongation of the period of recovery after intense 

 stimulation is demonstrated by the following experiments. 



