CH. IV] 



KOHLS METHOD. 



83 



the rates of absorption 1 . The actual volume of water 

 absorbed per unit of time may be obtained by calculation 

 from the length and diameter of the capillary tube. Or by 

 replacing the plant by a siphon delivering a known weight 

 of water per hour 2 . 



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



This apparatus, like the potometer, is a modification 

 of Sachs' instrument 3 . 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 tube abo fitted up as 



n 



h 



FIG. 16. Exp. 93. 



shown in fig. 16. The end, c, as before, takes the branch 

 br\ a takes a tube connected by a rubber tube with a 

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

 which is coarser than that used in exp. 92, and also 



1 Reciprocals may be got from published mathematical tables. 



2 See Darwin and Phillips, loc. cit. 



Physiologic (French Translation), p. 246. 



62 



