*' 



effects of radium rays in the soil i43 



Experiment 39 

 April I, 4 P. M. 



Unsoaked timothy grass {Phleiim -pratense) seed was sown on the 

 surface of the soil in two flower pots. In the center of the soil of 

 one pot was inserted the end of the glass tube containing RaBrg of 

 7,000 activity, to a depth of 15 mm. ; in the control pan the empty 

 glass tube. 



Both pots were watered by being set in a pan of water until the 

 top of the soil appeared entirely moistened. They were then cov- 

 ered with bell- jars. 



April 10, II 130 A. M. 



The seedlings in the radiated culture are slightly taller than those 

 of the control set, but the difference is not marked. 



April II, 5 P. M. 



There is no appreciable difference in the height of the plants in the 

 two pots. 



Summary 



When unsoaked oat grains were planted at distances of 7» 22, and 

 45 mm. from a sealed glass tube containing 10 mg. of radium bro- 

 mide of 1,500,000 X inserted into the soil, germination and subse- 

 quent growth were accelerated. The seeds farthest from the radium 

 were accelerated most, those nearest least. The root hairs on the 

 exposed seedlings appeared to be more numerous, and were 2-3 times 

 longer than normally. When seeds of Luptnus albus were exposed 

 in a similar way to the same radium preparation the growth of the 

 shoot was retarded, but the roots were from three to five times longer 

 than normally. This is in agreement with the results of Willcock 

 and of Zuelzer which indicate that tissues containing chlorophyll are 

 more sensitive to these rays than other tissues. Under similar condi- 

 tions the germination of seeds of Brassica alba was accelerated. 

 When seeds of Pisuni sativum were similarly exposed, using radium 

 of 10,000 X and the sealed glass tube of radio-tellurium, acceleration 

 of growth was produced by the radium rays, but none by the radio- 

 tellurium. Careful counting disclosed no significant difference in 

 the number of root-tubercles on the exposed plants and those of the 

 control culture. More careful observation has not confirmed my 

 earlier * statement to the contrary. 



* Bibliography, p. 71. No. 24. 



