90 



EFFECTS OF EXPOSING SEEDS 



120 

 110 

 100 



90 



80 

 70 

 6o 

 1 50 

 40 

 30 

 20 

 10 

 



10 



11 



12 



13 



14 



15 



16 



17 18 



/ 8 9 



Fig. 5. Acceleration of Growth of Wheat Following Exposure to a Rajs from 



Polonium. 



by exposure to the rays. A five days' exposure of Ltcfimis to radium 

 of 1,500,000 X retarded germination and growth, but did not appre- 

 ciably affect irritability, as shown by the fact that the plants still per- 

 formed their nyctitropic movements. Exposure in the radium-lined 

 cylinder (of much weaker activity, but permitting the a rays to act) 

 retarded germination and growth less than exposure to a stronger 

 preparation. The effect of the radium-coated rod of 25,000 x was 

 also less than that of the preparation of 1,500,000 x . Oats exposed 

 to this last preparation for a little over six and one half days were 

 greatly retarded in germination, and had their subsequent growth 

 completely inhibited. In the rod- and cylinder-exposures the a rays 

 were in large part available, as well as the /3 and y rays, but the 

 added effect of the a rays was not sufficient to compensate for the 

 weaker activity of the preparations. 



An exposure of dry wheat grains ( Triticum vulgar e) for ten days 

 to a rays by placing them in contact with a metallic rod coated with 

 polonium was followed at first by a slightly less rapid growth, and 

 then, eleven days after planting, by a more vigorous and rapid 

 growth than that of seeds similarly grown but not exposed. 



2. Effects on Growth of Exposing Seeds while Soaking 

 The object of the following experiments is to ascertain the effect 

 on germination and growth of exposing seeds during imbibition of 

 water to the rays of radium. 



