EFFECTS ON PLANT RESPIRATION 



197 



1. The sealed glass tube of RaBr^ of 10,000 activity. 



2. The sealed glass tube of radio-tellurium. 

 C. Control. No radium preparation. 



Over all was placed, in each tumbler, a piece of moist blotter. 

 Leading from each tumbler, through an air-tight rubber stopper into 

 a mercury bath, was a glass tube, graduated to i/ioo of a mm. 

 The entire tumbler in each case was immersed in water to insure 

 similar temperature conditions, and also to make the respiratory 

 chamber more surely air-tight. 



The rise of mercury, following the absorption, by the KOH solu- 

 tion, of the CO, given off, was taken as the index of both the rate 

 and the amount of respiration. The record of readings is given in 

 the following table, and in figure 49. 



Readings of the Scale^ Multiplied by lOO 



Time (Aug. 15) RaBr^, 10,000 X 



9:^5 



10: 15 

 11:15 

 12:30 



15 

 15 



74.25 = 0.00 

 4.00 

 70.25 

 67.25 

 64.00 

 62.25 

 59.00 

 57.00 



53-50 

 Total, 



3.00 

 3-25 

 1-75 

 3-25 

 2.00 



3-50 



20.75 



Radio-tellurium 



81.25 = 0.00 



2.00 



79-25 



77-25 

 75.00 

 74.00 

 72.00 

 70.00 

 67.50 



Total, 



2.00 

 2.25 

 1. 00 

 2.00 

 2.00 

 2.50 



13-75 



Control 



71.00 = 0.00 

 2.00 

 69.00 

 67.00 

 65.00 

 64.00 

 62.00 

 60.00 

 57-25 

 Total, 



2.00 

 2.00 

 1. 00 

 2.00 

 2.00 

 2-75 



13-75 



The radio-tellurium produced no effect that could be detected, 

 but a decided acceleration in respiration followed the exposure to the 

 rays from RaBr2 of 10,000 activity. 



Experiment 78 



This experiment was arranged as in No. 77, using sealed glass 

 tubes of RaBrg, of 1,500,000 and of 10,000 activity. In each respi- 

 rometer 20 grains of the wheat were used, with a total dry weight in 

 each case of .50 gm. 



