No. 504] PHYSIOLOGICAL EFFECTS OF RADIUM RAYS 175 



livered over the cultures, the seeds were found to have 

 germinated and grown uniformly under the control jar, 

 but, in the culture exposed to the emanation, the seeds 

 immediately under the funnel through which the emana- 

 tion was delivered had entirely failed to germinate. The 

 other seedlings of this culture were only very slightly less 

 vigorous than those of the control (Fig. 14). 



To further investigate the effects of this radioactive 

 air, five germinated seeds of L. albas with radicles over 

 10 mm. long were marked with India ink 10 mm. back 

 from the root-tip. These seedlings were then suspended 

 vertically, five under each bell-jar. The air, normal in 

 one jar, radioactive in the other, was forced into the bell- 

 jars by means of a rubber bulb, the blasts being given at 

 irregular intervals of from two to twenty-four hours. At 

 the end of the first twenty-four hours the average length 

 of the exposed radicles was 19.00 mm., and of the control 

 only 12.10 mm. At the end of the second twenty-four 

 hours the average lengths were, for those exposed 23.30 

 mm., for those unexposed, 12.70 mm. The curves of 

 growth for this experiment are given in Fig. 15, showing 

 the acceleration in rate of growth under the conditions 

 imposed. 



