152 RESEARCHES ON IRRITABILITY OF PLANTS 



alternately applied at equal distances to the right and to 

 the left of the leaflet. In one case the excitatory wave 

 was transmitted in a centripetal direction, that is to say, 



Table showing Difference of Velocity in Two Directions. 



towards the stem or main axis of the plant. In the other 

 case, excitation travelled outwards towards the tip of the 

 leaf or in a centrifugal direction. From a large number 

 of experiments carried out in this manner it was found that 

 the velocity is greater in the centrifugal direction. 



Summary 



By applying stimuli of constant intensity, and by 

 allowing proper intervals of rest, successive values of 

 velocity of transmission of excitation are obtained which 

 are constant. 



Consistent results are also obtained by the employment 

 of Differential Method for the determination of velocity of 

 transmission. The automatic records afford measurement 

 of time as short as "05 second. 



The highest velocity of transmission of excitation that 

 has been found in the petiole of Mimosa is 30 mm. per 

 second. 



In a sub-tonic tissue the velocity of transmission of 

 excitation is enhanced under increased intensity of stimulus. 

 The tissue becomes a better conductor of excitation in 

 consequence of previous stimulation. 



