AUTONOMIC MOVEMENTS IN SUCCULENTS 



333 



broken at the time of removal from the soil but measurements were not begun 

 until an abundant supply of fibrous roots had been formed. 



Method: Nos. 13 and 14 were sealed in separate bottles in the following way. 

 Each bottle was completely filled with water. A rubber stopper containing 

 three holes, one for the plant stem, one for a burette and one for a thermometer, 

 was cut into two pieces and then forced into place around the woody part of the 

 stem until the system was air-tight. The water in the burette rose above the 

 general level and was adjusted to a convenient height. The burette was of nar- 

 row diameter, being graduated to 0.01 cc. with a possibility of readings being; 

 estimated to 0.001 cc. 



Fig. 7. Correlation of movements of joints and changes in turgidity of the 

 plant. Solid line, movements. Broken line, water-content changes. June 28 

 to July 1, evaporation of average intensity. July 1-3, evaporation of unusually 

 high intensity. Two lowest graphs indicate temperature and light conditions. 

 See experiment 9. 



At the beginning and end of each period the entire bottle with the plant was 

 weighed for the determination of the loss from transpiration. Atmometers 

 of the Livingston type were used, for the measurement of evaporation. In 

 order to determine the amount of water taken up by the roots, the height of the 

 liquid in the burette was read at each period and the difference between the read- 

 ings, after it was corrected for contraction and expansion of volume due to tem- 

 perature changes, represented the amount of water absorbed by the roots. 



The correction for expansion and contraction was found by means of two 

 control bottles of the same capacity as the ones containing the plants. These 

 bottles were filled with water and fitted up in all respects like the ones holding 

 the plants. By means of twenty readings extending over several days the amount 

 of change in volume per degree, for the temperatures used, was found from meas- 

 urements of the changes in height of the water in the burettes and of the corre- 



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