148 EFFECTS OF RADIOACTIVE AIR ON GROWTH 



March 17, 9 : 30 A. M. 



The seedlings of the exposed culture are decidedly taller than 

 those in the control. 



This difference in height of the seedlings of the two cultures con- 

 tinued until March 24, when the experiment was discontinued. 



Experiment 41 

 The object of this experiment is to ascertaiji the effect of growing 

 seeds of timothy grass {Phleum p7'atense) in the apparatus described 

 for Experiment 40, /. c, in an atmosphere containing the radium 

 emanation, but exposed more directly to the rays resulting from the 

 decay of the emanation. 



April I, 2 : 30 P. M. 



The experiment was set up as described in Experiment 40, except 

 that the air and the emanation were delivered at a distance of only 

 about 5 mm. above the seeds. Special care was taken to have the 

 illumination equal on all sides, and both the light and the moisture 

 conditions as nearly as practicable the same for both the exposed 

 and the control cultures. 



April 6, 8 : 30 A. M. 



Germination has begun in both cultures, but is more advanced in 

 the control pan. 



April 10, 10 A. M. 



In the exposed culture the plants are shorter and lighter colored 

 on the side nearest the delivery of the emanation, and increase in size 

 toward the opposite side of the pan. They manifest a slight photo- 

 tropic curvature. 



The plants of the control culture are of uniform height, and also 

 have a slight phototropic curvature like those exposed. 



The growth of the seedlings nearest the point of delivery of the 

 emanation has been retarded. The cultures were photographed on 

 April 12 (figure 29). 



This experiment was repeated with entirely confirmatory results. 



Experiment 42 

 In order to test the effect on the germination and growth of the 

 timothy seed, when grown in an atmosphere containing the radium 



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