144 EFFECTS OF RADIUM RAYS IN THE SOIL 



The growth of oats exposed in the same way (10,000 x ) was 

 accelerated, but bean seeds [Pkaseolus vulgaris) exposed to radium 

 (1,500,000 x) in the sealed tube, and also to four coated rods 

 (25,000 x) had their germination and the growth of the seedlings 

 retarded. Exposure to the rods (low activity) produced less retarda- 

 tion than did exposure to the preparation in the glass tube (high ac- 

 tivity), though in the former case the a rays escaped for very short 

 distances into the soil. 



Exposure of wheat {Triticum vtilgarc) to radium of 1,800,000 x 

 and 1,500,000 X , and to radio-tellurium, each in a sealed glass tube in- 

 serted into the soil, was followed by acceleration of germination and 

 growth. The amount of acceleration was about equal in each of the 

 three exposed cultures, though slightl}^ in excess in the culture ex- 

 posed to the radio-tellurium, where the amount of the salt was larger 

 than in the radium cultures. I am unable to explain how physiolog- 

 ical effects can be obtained with radio-tellurium in a sealed glass 

 tube, for this substance gives off only a rays, and these are not 

 thought to be able to pass through the glass walls of the tube. The 

 results, however, were constant and decided, leaving not the slightest 

 doubt as to the physiological efficacy of the preparation. 



When seeds of timothy grass were sown on the surface of soil 

 into which a sealed glass tube of radium bromide of 7,000 x was in- 

 serted to a depth of about 10 mm. below the surface, germination 

 and growth were very slightly accelerated. 



Whether the acceleration of growth produced by inserting sealed 

 glass tubes of radioactive preparations into the soil is due to the direct 

 action of the rays, or to ions which they may possibly form in the 

 soil-solution, remains to be demonstrated. If to the former, then the 

 result must be attributed largely to the gamma rays, for the alpha 

 rays do not leave the glass tube, and the beta rays would be stopped 

 by at least one centimeter of moist soil. The gamma rays, however, 

 on account of their high penetrability, might be effective through as 

 much as one foot of moist soil. 



Fischer ^ has shown that hydrogen ions and hydroxyl ions, 

 whether of acids or of strong alkalis, stimulate germination. In his 

 experiments the ions acted explosively, as he described it, a marked 

 effect being produced by them by an exposure of one half a minute, 

 a maximum stimulation on two minutes, while killing began with 

 only four minutes' exposure. If the radium rays produce ionization 



