CH. V] ISOTONIC COEFFICIENT. 127 



spirals and can then be cut up into some 7 or 8 rings, 

 b, fig. 23 : these are delicate tests of changes in turgescence 

 since a small increase or decrease in the curvature of the 

 turgescent tissue is at once perceptible. Thus s is in too 

 strong a solution, w is in too weak a solution, while b is 

 in one that almost exactly balances the osmotic power of 

 the cell sap. 



The process with Ricinus is a little more troublesome ; 

 the hypocotyl is split in 4 or more longitudinal portions, 

 and the form of each is traced with a paint-brush (which 

 answers better than a pencil) on paper. We now have a 

 number of curved bits of tissue (whose form is kno^vn) 



Fig. 24. Exp. 148. 



each one of which must be placed in a solution of a 

 different strength. These solutions are made according 



