CHAPTER IV. 



TRANSPIRATION. 



Section A. Absorption of water by transpiring plants. 

 Section B. Loss of weight due to transpiration. 

 Section C. Stomata, Bloom, Lenticels. 



Section A. Absorption. 



(92) Potometer\ 



In the first series of experiments (Section A) the rate 

 of absorption of water by transpiring plants under varying 

 circumstances is to be observed. This may be done with 

 potometer as shown in fig. 13. Of the three openings of 

 the potometer, A and B are closed by rubber corks ; that 

 in 5 is perforated by a thermometer-tube of about 0'3 mm. 

 bore : the tube should just project beyond the cork on the 

 inside and should have a total length of 7 or 8 inches. 

 The eiid A is closed by an unperforated cork, while to G is 

 fitted about 4 inches of rubber tubing, of which 2 inches 

 project beyond the end of the tube. The cork B should 

 first be fitted in, then fill the potometer with water and 



1 Darwin and Phillips, Cambridge Philosoph. Society, Vol. v. 1886. 



