AUTONOMIC MOVEMENTS IN SUCCULENTS 



341 



in place firmly. For the measurement of the longitudinal changes the end of 

 the curved lever was bent up until it rested in the same horizontal plane with 

 the pen and its end then placed on the tip of the joint. 



Results: The records from the tracings have been transferred to coordinate 

 paper and appear in figure 11. The recording pen magnified the changes about 

 three times and the actual maximum difference is size between day and night 

 was about 0.15 cm. in both the radial and longitudinal directions. 



All of the records show an expansion for the day and a contraction for the 

 night. The changes on cloudy days were less than on bright days. 



B 



Pen trace. 



100" 



80° 



Apr. 27 



Apr. 28 



Apr. 29 



Apr. 20 



Apr. 21 



Apr. 22 



Apr. 23 



Apr. 24 



Apr. 25 



Fig. 11 A. A copy of an automatic pen trace (topmost curve) showing radial 

 contraction and expansion of a joint. See experiment 11. 



Fig. 11 B. A copy of an automatic pen trace (topmost curve) showing longi- 

 tudinal expansion and contraction of a joint. Two lowest graphs indicate 

 temperature and light conditions. See experiment 11. 



Direct determinations of the water-content were attempted 

 by heating joints to constant weight at 100°C. and calculating 

 the original water-content per gram of dry weight. The individ- 

 ual variations of the joints were so great that any day to night 

 changes were masked. However, the results of experiments 10 

 and 11 show that a difference in water-content does exist and there 

 is no need of further proof that turgor is greatest in the day 

 time when normal conditions exist. Thus the shorter period 

 movements, as well as the longer ones, have been shown to be 

 due to turgor changes. 



