n6 RESEARCHES ON IRRITABILITY OF PLANTS 



•oi second. It will be seen that the responsive movement 

 begins to occur between the tenth and eleventh dots, and 

 very near the latter. There are thus 10*9 spaces, each of 

 the value of - oi second, and the latent period is therefore 

 •109 second. In order to test to what extent successive 

 experiments might give concordant results, I took a second 

 record with the same specimen, which appears in fig. 67 

 as the lower of the two, having given the plant an interval 

 of rest of 20 minutes after the taking of the first record. It 

 will be seen that the second record is essentially a replica 

 of the first, thus demonstrating that with proper precautions 



Fig. 68. — Record of highly excitable specimen, taken with 

 100 D.V. recorder on a slowly moving plate. 



successive experiments on the value of the latent period will 

 give results which are of extraordinary constancy. 



By making the travel of the recording-plate very rapid, 

 the successive dots become more widely spaced and the 

 minute time-intervals involved are made more conspicuous. 

 But this has the disadvantage of rendering the flexure of 

 the curve representing the responsive movement less abrupt, 

 making the exact point of initiation of response somewhat 

 more difficult to discriminate. Going, on the other hand, to 

 the opposite extreme of making the travel of the recording- 

 plate slow, the flexure of the curve becomes more abrupt, 

 enabling us the better to detect the point of initiation of 

 the responsive movement. The time-dots, however, are 

 now closer together. This can be seen in another record 

 (fig. 68) obtained with a vigorous specimen. Here the 



