OXYGEN EFFECT WITH X-RAYS 



273 



modify the aberration frequency, thus indicating that oxygen itself has 

 no effect on the recovery process. There seems to be Uttle question that, 

 under the experimental conditions utilized, oxygen diffuses very rapidly 

 into the cells and is present during the recovery process. This is shown 

 by the fact that the introduction of oxygen during irradiation causes a 



TABLE 2 



Experiments on the Introduction of Oxygen during X-Irradiation 

 OF Tradescantia Inflorescences 



(All exposures of 300 r at 300 r per min) 



pronounced increase in aberration frequency. This latter result is also 

 important in providing additional evidence that oxygen, to be effective, 

 must be present during the actual irradiation and that there is little or 

 no latent period between the introduction of the gas and its effect in 

 terms of increased aberration production. Other experiments have also 

 demonstrated that a pre-exposure of buds in pure oxygen before they are 

 irradiated in helium has no effect. 



From all these observations, it seems clear that the effect of oxygen 

 itself is an indirect one, presumably arising from the production by x- 



