EFFECTS OF RADIUM RAYS IN THE SOIL I37 



March lo, 5 P. M. 



I now changed places with the radium-tube and the empty tube, 

 placing one end of the radium-tube in the center of the soil of the 

 culture that had served as the control. This pot was labeled CR, 

 and the other pot R. Five days later the control plants (CR), under 

 the influence of the radium, averaged nearly as tall as those first 

 radiated. Thus, by changing the radium-tube back and forth from 

 time to time, one can accelerate either culture at will (figure 25). 



Experiment 33 

 Repetition of Experiment 32, using seeds of Lufinns albus. 



March 19, 11 130 A. M. 



Six unsoaked seeds of L. albus were planted about 5 mm. deep 

 around the margin of a 5-inch pot. All the seeds were placed with 

 the hypocotyl facing the center of the pot and pointing downward. 

 In the center of the soil was inserted one end of the sealed glass tube 

 containing RaBr2 of 1,500,000 activity, to a depth of about 10 mm. 



Control pot with six seeds and empty glass tube. 



March 24, 11 : 30 A. M. 



In the radium-culture no seeds are up. Two of them are just 

 beginning to lift the soil. 



In the control culture four seeds are up, from 10 to 15 mm. high. 

 Two other seeds are just coming through the soil. 



On March 26 only one exposed seed was up, with the hypocotyl 

 10 mm. high, while 5 of the control seeds were up with an average 

 height for the five of 19.60 mm. The radium and empty tubes were 

 removed from the soil. 



Six days later (March 30) only two of the exposed plants had 

 come up. Their average height was 30 mm. Five of the control 

 seeds were well up, with an average height of 45.60 mm. 



The plants were all removed from the soil. On the two radiated 

 plants the primary and secondary 'roots were very slightly developed, 

 but on the control plants the secondary roots were long and numerous, 

 and the primary root was from three to five times as long as in the 

 plants exposed to the radium. 



Experiment 34 

 Repetition of Experiment 33, using white mustard {Brassica alba) 

 seeds instead of lupine. 



