EFFECTS OF EXPOSING SEEDS 



III 



greatly retarded (figure 9), and roots were fewer in number, shorter, 

 thick, and club-shaped, with the slightly more numerous root-hairs 

 nearly twice the normal length. The root-tips of the exposed plant- 

 lets were of a decidedly darker color than those of the control. 



4. Effect of Duration of Exposure and Degree of 



Activity 



In the preceding experiments it has become more and more 



clearly evident that the effect of exposure to radium rays varies, as 



Koernicke also found, with the duration of the exposure and the 



degree of activity of the radium. The purpose of the following six 



experiments was to confirm this fact, and get more accurate data on 



the relation between the duration, the degree of activity, and the 



effect produced. 



Experiment 26 



The object of the following experiment is to ascertain the effect 

 on the germination and growth of corn {Zea Mays) of exposure for 



120 



10 



11 12 13 



Day of month 



15 



Fig. II. Effect on the Growth of Zea Mays of Exposing the Grains, before Plant- 

 ing, iomU Hours, to Rays from Radium of Different Degrees of Activity. 



