﻿main leaf-stalk acts, and the entire leaf 

 sinks. If the stimulus has been given with 

 sufficient force, or by means of a match flame 

 instead of the forceps or scissors, the move- 

 ment will be taken up in turn by the leaves 

 above and below the one treated. The reac- 

 tion of the plant is most rapid in specimens 

 growing vigorously, and standing in moist 

 air at a temperature of 30-35° centigrade. 



It may be noticed that a short time elapses 

 between the action of the stimulus from the 

 scissors or flame and the reaction of the leaf- 

 let. This is termed the latent period and 

 amounts to slightly less or more than a sec- 

 ond according to conditions. The experi- Transmission 

 ments also have demonstrated that the effects °* stimuli 

 of a force applied to one part of the plant 

 may be transmitted over its entire body, which 

 is often a yard or a meter in length. If care- 

 ful note of the time is made between the appli- 

 cation of the stimulus to the plant and the 

 reactions in different portions of the plant, 

 together with accurate measurements, it will 

 be found that the impulse or force set in mo- 

 tion by the stimulus travels at the rate of 

 eight to twenty-five millimeters (% to 1 inch) 

 per second under favorable circumstances. 



As the plant stands in the quiet atmosphere 

 on a warm morning, a breath of air or the 

 smallest drops of water striking the blades 



