76 KOHL'S METHOD. [CH. IV 



the rates of absorption'. The actual volume of water 

 absorbed per unit of time may be obtained by calculation 

 from the length and diameter of the tube T. Or by re- 

 placing the plant by a siphon delivering a known weight 

 of water per hour^ 



(93) Kohl's method [slightly modified]. 



This apparatus, like the potometer, is a modification 

 of Sachs' instrument. Here the index is not a bubble of 

 air, but the column of air which travels onwards as the 

 water is absorbed. We use a potometer fitted up as 



Fig. 14. Exp. 93. 



shown in fig. 14. The end, c, as before, takes the 

 branch hr; a takes a tube connected by a rubber tube 

 with a funnel /, and closed by a clamp ; h takes a glass 

 tube connected with a horizontal tube h, which is coarser 



' Beciprocals may be got from published mathematical tables. 

 2 See Darwin and Phillips, he. cit. 



