Qzj. EFFECTS OF EXPOSING SEEDS 



Experiment 9 

 March 19, 6 P. M. 



Seeds of timothy grass were arranged along 8 radii of a circular 

 piece of blotter in a Zurich germinator and a tube of RaBrg (7,000 x ) 

 was placed vertically over the center with the end containing the 

 radium resting on the seeds. 



Control with empty tube, and both cultures placed to germinate 

 in the dark-room. 



March 23, 10:30 A. M. 



The seeds have germinated quite uniformly in the control culture, 

 averaging about 3-6 mm. high. 



In the radium culture the germination is similar to that in the con- 

 trol, except under the radium-tube, where germination, though not 

 entirely inhibited, has been greatly retarded, the seedlings not averag- 

 ing more' than 1-2 mm. high for a radius of about 5 mm. from the 

 center of the tube in all directions. 



The glass tubes were removed and both cultures were placed in 

 the laboratory in front of a window. Cylinders of blotter were 

 placed around the culture dishes to prevent phototropic curvature. 



March 26, 11 A. M. 



The plants in both cultures are of about the same height, except 

 in the radium culture, where those in the center, directly under the 

 radium, are noticeably shorter than the others, and the height in- 

 creases rather abruptly from the center toward the circumference. 



The tubes were removed and the cultures left to develop further. 



March 30, 3 P. M. 



The retarded seedlings in the center of the radiated culture have 

 reached about the average height of the others, and the difference 

 in the average height of the seedlings in the two cultures is very 

 slight. The balance, if any, is in favor of the radiated set being 

 slightly taller. 



March 31, 5 P. M. 



The radiated seedlings average decidedly taller than the con- 

 trol set. Thus, following exposure to the radium, there has been 

 at first a retardation of germination and growth, then, after the 

 removal of the radium, an apparent recovery and subsequent 

 acceleration. 



