EFFECTS OF RADIUM RAYS IN THE SOIL I45 



in the mineral solutions in the soil then these ions would act as a stimu- 

 lus to plants growing there, and, under suitable conditions, cause an 

 acceleration of growth. It is not improbable that the results recorded 

 above are due to a combination of both causes, that is, to the direct 

 action of the gamma rays combined with that of ions produced by 

 the rays in the soil-solution. 



Bibliography 



I. Fischer, Alfred. Wasserstoff- und Hydro^cylionen als Keimungsreize, 

 Ber. Dent. Bot. Ges. 25: 108. 1907. 



II 



