772 



THE AMERICAN NATURALIST [Vol. XLII 



of the rate of respiration. Under such conditions, and 

 with radium of 10,000 as well as 1,500,000 activity, the 

 result was always an acceleration of respiration, as is 

 shown in Fig. 11. It is probable that, under certain con- 



1 1 1 1 



Experiment 79. 









ofg 



ct of radt 



y wheat. First 8 h 





































Jja».. 







































>:30 10.30 11:30 12-.W 1:30 2:30 3:30 4:30 5:30 

 Time 



ditions of exposure, the rays would retard or completely 

 inhibit respiration. 



In order to test the influence of the rays on alcoholic fer- 

 mentation, mixtures of commercial yeast in ferementation 

 tubes were exposed to the rays. A piece of compressed 

 yeast weighing 1 gm. was thoroughly mixed in 100 c.c. 

 of tap-water, and equal portions of this mixture were 

 placed in fermentation tubes. Into these tubes were 

 placed sealed glass tubes containing radium bromide of 

 activities 7,000, 10,000 and 1,500,000. A fourth fermen- 

 tation tube with no radium served as a control. The rate 

 of fermentation was measured by the rate of evolution 

 of the gas. The results of all experiments indicated a 

 decided acceleration of fermentation under the influence 

 of the rays, and, as the curves in Fig. 12 clearly show, the 

 amount of acceleration is in direct proportion to the ac- 

 tivity of the radium. 



No reference has yet been made of the fact that radio- 

 activity is a factor in the normal environment of plants. 



