EFFECTS OF RADIOACTIVE AIR ON GROWTH I47 



of this Memoir. The details of the method are given in connection 

 with the experiments that follow. 



Experiment 40 

 Object : To ascertain the effect of germinating and growing tim- 

 othy grass [Phletwi pratense) seeds in an atmosphere containing 

 the radium emanation. 



March 12, 11 A. M. 



Unsoaked timothy seeds were sowed in a pot of earth (thinly cov- 

 ered with the soil), and placed to germinate and develop under a bell- 

 jar. From a hollow cylinder lined with " Lieber's radium-coating" 

 there passes a glass tube through the upper tubulure of the bell-jar and 

 down into the latter, ending, at the side of the pot of soil, in a dove- 

 tail gas tip, at a height of about 20 mm. above the surface of the soil. 

 From the opposite side of the pot leads another glass tube through 

 the bottom tubulure of the bell-jar to a suction pump. By this means a 

 current of air containing the emanation from the radium-lined cylinder 

 spreads out over the surface of the soil, and converges to the outlet 

 tube, passing thence out of the jar. A control apparatus was sim- 

 ilarly arranged, connected with the same suction pump, but with no 

 radium tube attached (figure 28). 



Fig. 29. Experiment 41. Retardation of Growth of Timothy Grass bj exposure 

 to Air which has passed over Lieber's Radium Coating, and thus contains Radium 

 Emanation. 



March 15, 4 : 30 P. M. 



There are no signs of germination in either pot. 



March 16, 9 : 30 A. M. 



The seeds in both pots have begun to germinate, but those 

 exposed to the emanation appear to be slightly further advanced 

 than the control. 



