ON Drosera rotundifolia 



11 



heavy line; the growth of the adaxlal side is shown by the Hght 

 line. The calculated growth of the median section of the tentacle 

 is given by the broken line. The time is plotted on the abscissae; 

 each space is thirty minutes. The changes in length are plotted 

 on the ordinates; each space represents 0.02 mm. The reaction 

 time is not indicated. The cross shows when the bending was 

 completed and when unbending began. It is evident from the 

 figure that the inflexion of the tentacle is produced by a con- 

 siderable acceleration of the rate of growth on the abaxial side 

 and in the median section. The unbending is more gradual and 

 takes six times as long as the bending. Moreover the unbending 

 is produced by a similar but less intense acceleration of the growth 

 on the adaxial side and in the median section together with 

 contraction of the abaxial side during the beginning of the process. 

 The reaction of another tentacle is shown in Table II and Fig. 



Table II 



Fig. 5. A graph representing the bending and unbending of a tentacle, drawn 

 according to data in Table II, and on the same scale as Fig. 4. 



