DETERMINATION OF THE LATENT PERIOD 121 



period shorter than - o8 second or longer than -12 second 

 in summer may be regarded as rather exceptional. 



Tabular Statement of Values of Latent Period L in 

 Numbers of Different Specimens of Mimosa, 



The shortest latent period that I have come across 

 is *o6 second obtained in summer and when the temperature 

 was specially high. The longest in summer was -14 second. 

 Most specimens have a latent period not appreciably 

 differing from -i second. This may be regarded as approxi- 

 mately the average value for summer. In winter and with 

 sluggish specimens the latent period may be prolonged to 

 a value of something like twice as much, that is to say, 

 •2 second, more or less. 



Summary 



Latent period of Mimosa may be determined with 

 great accuracy by means of Resonant Recorder. This 

 enables the measurement of time-interval shorter than 

 •005 second. 



Error due to inertia is reduced to a minimum on account 

 of extreme lightness of plant-recorder, which is nearly a 

 hundred times lighter than muscle-recorder. 



Successive values of latent period with the same speci- 

 men are found to be constant. The results are not modified 

 by employment of different recorders. 



The shortest value of latent period given by a vigorous 

 Mimosa leaf in summer is *o6 second, the average value 

 being 1 second. 



The latent period of leaf of Ncptunia oleracea is "6 second. 



