EFFECTS OF EXPOSING SEEDS 



125 



The results are in perfect accord with the hypothesis, and with 

 the results of other experiments. The rate of growth is seen to vary- 

 inversely with the duration of exposure (figure 21), and to decrease 



Fig. 20. Experiment 27. Root Systems of Seedlings of Lupinus albus from 72- 

 Hour and from Control Cultures Shown in figure 19. 



most -rapidly as the activity of the radium increases. The experi- 

 ment was continued until all the hypocotyls ceased growing in all 

 four cultures. 



