380 PLANT RESPONSE 



The normal rate of suction is now re-established, as seen in 

 the fact that the record becomes horizontal. 



(b) Effect of warm water. — I next tried the effect on the 

 same specimen of water at a higher temperature, falling by 

 degrees to the temperature of the room. We should expect 

 in such a case, to obtain the excitatory effect of rise of 

 temperature, with subsequent approach to the normal, with- 

 out any reversal, indicative of the transition from exaltation 

 to depression, such as was observed in the case of application 

 of cold. From the second and lower of the two curves 



FlG. 162. Record, obtained by Method of Hydraulic Balance, of Successive 

 Effects of Cold and Warm Water 



shown in fig. 162, it will be seen that this is the case. 

 The curve at first rises abruptly, and it continues to rise, 

 though with decreased speed, till, when the temperature of 

 the vessel is once more normal, it becomes horizontal, 

 indicating the resumption of the original rate of suction. 



We have thus seen, by three different methods of inquiry 

 those namely of the Unbalanced Shoshungraph, the Hydro- 

 static Balance, and the Hydraulic Balance — that the re- 

 cords, though of different forms, exhibit effects of which the 

 interpretations are identical. For delicate experiments, the 



