204 



EFFECTS ON PLANT RESPIRATION 



These readings indicate, as in the preceding experiments, a re- 

 tardation of respiration hy the radium of 1,500,000 activity, but the 

 volumes of gas evolved by the seeds exposed to radium of 10,000 

 activity and to radio-tellurium exceed the volume given off by the 

 control seeds- 



bo 



i 2 



^ 



Summary 



When a sealed glass tube containing .52 gm. of radium bromide 

 of 10,000 X is laid over, and in contact with soaked wheat grains 

 placed to germinate, an acceleration of respiration results, but no 

 effect could be detected when the grains were similarly exposed 

 to radio-tellurium in a sealed glass tube. A like exposure to rays 

 from 5 mg. of radium bromide of 1,500,000 x also resulted in an 

 acceleration of respiration, but not to so great a degree as was caused 

 by the preparation of 10,000 activity. 



If the grains were exposed dry, before soaking, for 54 hrs. to rays 

 from the radium of 1,500,000 x , their respiration was at first retarded, 

 but this was followed by recovery and marked acceleration. 



