340 



EDITH BELLAMY SHREVE 





$ 



/ 



Fig. 10. A device for automatically measuring radial expansion and con- 

 traction of joints. See experiment 11. 



Experiment 11. • 



Object: The discovery of any longitudinal and radial contraction which may 

 take place from day to night, under normal conditions. 



Material: Plants Nos. 18 and 19. They were both potted plants having verti- 

 cal joints. No. 18 had a joint which was grown in the green-house and No. 19 

 had made its entire growth in the open. 



Method: The apparatus which was used is shown in figure 10, where it is in 

 the position to measure radial expansion and contraction. The part of the 

 joint immediately opposite the point of contact of the lever which moves the 

 recording pen, was imbedded in a plaster of paris jacket, so that it might be held 



