126 hofmeister's experiment. [ch. V 



to have taken on a permanent curve. This is only another 

 way of demonstrating what is showu in experiment 158 : 

 the cortical tissues on the convex side of the shoot are 

 forcibly elongated by the Tjending, and being imperfectly 

 elastic do not return to their original length, thus pro- 

 ducing a distortion of the shoot. 



To get an accurate notion of what occurs in this 

 experiment it is desirable to measure the radius of 

 (1) the curvature forcibly produced, (2) of the permanent 

 curvature remaining. This may be done with Sachs' 

 cyclometer, which consists of a number of concentric 

 circles drawn on a board. By applying the shoot to 

 the board, the circle which corresponds to it most nearly 

 in curvature can be ascertained and noted. In our 

 Laboratory we have two boards, one bearing circles 

 whose radii range from 1 to 20 cm. in length : while the 

 circles on the other range from 21 to 45 cm. 



(160) Hofmeister's experiment^. 



This is in principle the same as experiment 159; it 

 has, however, a certain classic interest which makes it 

 worth repeating. 



What is needed is a vertical turgescent shoot fixed 

 firmly at its lower end : it may be either a plant growing 

 in a pot, or a shoot fixed into a clamp by its basal end. 

 In either case the base of the shoot is smartly struck with 

 a light stick so as to produce violent curvature of the free 

 end of the shoot towards the side which is struck. The 

 consequence is the same as that in experiment 159, 



1 Beriehte d. k. Saclis. Gesell. d. Wiss. 1859. 



