TORSIONAL ROTATION 379 



and of condition of turgor modify the circumnutation of the 

 twining shoot. The effect of these different factors on the 

 movement of the shoot will be presently considered in 

 greater detail. 



Fig. 214. 



Fig. 215. 



Fig. 214. Method of measurement of Circumnutation of a 



twining shoot. 



Fig. 215. Measurement of relative activities of successive 

 internodes. i', i", i'", indices fixed at different nodes. 



Experiment 202. Torsional rotation round the vertical 

 axis. — The observation was continued the next day with 

 the same plant with this difference, that the horizontally 

 inclined portion of the stem was now held erect by means of 

 a long and thin piece of string passing over a pulley, the 

 end of the string being attached to a suitable counterpoise ; 

 the string itself was practically torsionless. A fibre of 



