Page:Popular Science Monthly Volume 74.djvu/229

Rh

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 albus) 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, 0 hours (control). The size of the largest seedling in the pan at the left doubtless indicates that the seed