RADIUM RAYS 



225 



Fig. 1. 



seeds, together with ten unexposed, but otherwise similarly treated 

 seeds, were planted in soil in pots. The relative amount of growth in 

 the two cultures at the end of five days after planting is illustrated in 

 Fig. 2, where R is the culture exposed to the rays, and C the control 

 (unexposed) culture. The growth of the root system was also greatly 

 retarded by this treatment, and the root hairs on seedlings from 

 exposed seeds were much longer than normally. 



The effect of duration of exposure on the germination and growth 

 of lupines (Lupinus alius) is shown in Fig. 3. The activity of the 

 radium was the same in each case, 1,800,000, the seeds were exposed 

 dry, and the length of exposure, from left to right in the figure, was 

 72 hours, 50 hours, 26 hours, hours (control). The size of the 

 largest seedling in the pan at the left doubtless indicates that the seed 



VOL. LXXIV. 



-16. 



Fig. 2. 



