AUTONOMIC MOVEMENTS IN SUCCULENTS 



305 



Thermograph records were taken, and have been presented 

 in the accompanying figures. An arbitrary and very crude 

 method for indicating changing light conditions has been adopted. 

 A convenient distance was chosen as the height to represent the 

 light conditions in the open when the sky is clear and the sun- 

 light falls directly on the plants; one-half of this amount repre- 

 sents complete cloudiness or the shade within the laboratory. 

 No attempt was made to indicate anything beyond the grossest 

 changes in light intensity, such as are caused by partial or inter- 



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Fig. 3. Movements of Opuntia versicolor under three conditions of water 

 relations. See tables 2-5. Plants Nos. 4, 11, and 12 (solid line) are of normal 

 turgidity throughout the experiment. Soil continuously wet. Plant No. 1 

 (broken line) is of normal turgidity at the start of the experiment. Soil is dry- 

 ing out. Plant No. 8 (dotted line) is recovering from a previous short desicca- 

 tion period. Soil continuously wet. 



mittent cloudiness. A clear day is represented by a straight 

 line from sunrise to sunset regardless of the fact that the intensity 

 changes from hour to hour. 



Experiment 1. March 8-9, 1914. 



Object: The measurement of day and of night movements of a plant under 

 green-house conditions. Water-content of soil high. 



