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G. M. FRANK AND A. D. SNEZHKO 



oxygen naturally depends on the rate of diffusion from the external 

 medium and it may be supposed that the effect of the radiation which 

 leads to a depression of the rhythm simultaneously disturbs conditions 



1 min 



Fig. 6. — Change of rhythm in a bean root as the result of irradiation. Dose, 10,000 r. 



1, before irradiation; 



2, during irradiation (the arrows indicate the beginning and the end of irradiation) 



3, 3 lir after the end of irradiation; 



4, 5 hr after the end of irradiation ; 



5, 7 hr after the end of irradiation ; 



6, two days after irradiation. 



of oxygen diffusion from the outside. The question, however, is not 

 only one of diffusion transfer, but also of oxygen circulation phenomena 

 associated with the continuous motility of the protoplasm — the pro- 

 tof)lasmic streams. 



When comparing free oxygen level and rhythmic activity, one can 

 consider the depression of rhythmic activity to be an indirect result of a 

 decrease in free oxygen level. This is proved by the very start of the 

 effect and measurements taken directly under the beam. Depression of 

 rhythms sets in, practically at the very first minute after irradiation 

 when the free oxygen level has had not time to decrease. A decrease of 



