24; 



Fig. I. Method of demonstrating the difference in transpiration between the 

 upper and under side of the leaf by means of hygrometers. 



laboratory we have for a number of years made use of the ap- 

 paratus illustrated in figure 3, which consists of a wooden 

 stand mounted on legs, as shown in the illustration. This stand 

 supports a large bell glass containing two apertures and in the 

 center of the wooden stand there is a hole about one-half inch 

 in diameter through which the plant is inserted into a tube be- 

 low. The stem of the plant is forced down through the cork 

 stopper into the tube containing water. A piece of flexible 

 rubber cloth is tied around the bottom of the bell glass. The 

 stem of the plant is put through a slit in the rubber cloth which 

 is fastened to the plant securely by means of thread. From the 

 lower end of the larger tube containing the stem of the plant 



