148 RESEARCHES ON IRRITABILITY OF PLANTS 



transmission of excitation through a distance of 10 mm. 

 was here 1*32 second when the plant was fresh ; when the 

 specimen was fatigued the period of transmission through 

 the same distance was prolonged to 17 second. 



Table II. — Effect of Fatigue on Velocity of Transmission. 



The effect of fatigue is also here depicted in an interesting 

 manner in the records of the responsive movements them- 

 selves. In the upper record of the fresh specimen the 

 movement is seen to have been vigorous, by the comparative 

 erectness of the curve and the distance between the succes- 

 sive dots, representing the amount of the excitatory fall 

 during periods of one-tenth of a second. The lower curve 

 offers a marked contrast in both these respects. 



Effect of Temperature 



If the phenomenon of transmission in the plant is 

 one of protoplasmic change, then any factor that causes 

 physiological variation must have a corresponding influence 

 on its velocity. One such cause of physiological variation 

 is found in change of temperature. If, on the other hand, 

 the propagation had been merely of a hydrostatic blow, 

 then a change of temperature would not have had any 

 marked effect upon it. Thus the accurate determina- 

 tion of the influence of temperature upon velocity of 

 transmission becomes an important consideration in dis- 

 criminating between the excitatory or mechanical nature 

 of the transmitted change. 



I will now proceed to give quantitative results as to 



