242 MINNESOTA BOTANICAL STUDIES. 



rent of air from the plant chamber. From the first the curren- 

 passes into the second flask containing about 30 c. c. of the 

 acid. From the second flask the current passes on through a 

 16 cm, U tube filled with calcium chloride. Rubber stops and 

 glass connections are used in each case. The acid in the first 

 flask was found to take up nearlj'- all the moisture for the first 

 four hours of an experiment. What passed over was taken up 

 in the second. Repeated experiments were made and even 

 where a large leaf surface was used the calcium chloride in the 

 U tube after twenty-four hours was found almost as dry as 

 when it was put in. The calcium chloride and sulphuric acid 

 were renewed every twelve hours. 



After several observations had been made on the trans- 

 pirations of the leaves and internodes another fruit (No. 2) 

 was taken to determine its rate of transpiration or loss in 

 weight after it had been cut from the vine. One of the same 

 stage of development as the one on the first balance was se- 

 lected and its stem cut 6 cm. from the fruit. This portion of 

 the stem attached to the fruit was immediately immersed in 

 water in a test tube and the test tube sealed around it to pro- 

 vent evaporation of the water. The fruit and test tube 

 with water were now placed on the decrease pan of the regis- 

 tering balance. 



The registering balance was arranged to record decrease by 

 placing the fruit on the pan receiving the weights from the 

 holder. At the beginning of an experiment for taking decrease 

 the scale was balanced by weights in the other pan. Whenever 

 a decrease of such amount as to close the circuit took place the 

 equilibrium was restored by a weight dropping on the decrease 

 pan. The observations on the decrease of Fruit no. 2 were 

 carried on during ten days during five of which the stem was 

 immersed in water as described above. During the remaining 

 time observations were made on the decrease of the fruit after 

 it had been cat off from all supply of moisture. 



At the beginning of the experiments, September 22, 1 gram 

 weights were used in the registering balance, but with the 

 rapid rise of the increase to 1 gram per minute, it was found 

 necessary to substitute 2 gram weights, to allow time for 

 the balance to come to rest in the intervals. 



It was found convenient to begin and end the day at 8 a. m. 

 since this usually marked a period of equilibrium in the plant: 

 increase had ceased and decrease would set in shortly after 

 that hour. 



