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was poorly exposed. There is usually more or less difference in the 

 resistance of individuals, but never as much as that apparently indi- 

 cated, in the 72-hour culture. This and similar experiments confirm 

 the results of Koernicke and others that the effect varies directly with 

 the duration of exposure. 



Fig. 3. 



The relative effect of preparations of different activities is illus- 

 trated by the following typical experiment. Three sets, a, b and c, 

 of six dry seeds of the white lupine were exposed to rays from sealed 

 glass tubes of radium bromide by laying the tubes in contact with the 

 hilum edges of the seeds. Care was taken to have the radium salt dis- 

 tributed evenly along the bottom of the horizontally placed tube. The 

 activities of the preparations were: a, 1,800,000; h, 1,500,000; c, 

 10,0-00. A fourth set, d, served as a control. All exposures were for 

 91.5 hours. The seeds were then sown in soil in pots, and the com- 

 parative amounts of growth in the four cultures are shown in Fig. 4. 

 The activity decreased from left to right. It is clearly demonstrated 

 that the stronger the activity the greater the amount of retardation, 

 under the conditions of the experiment. 



Fig. 4. 



An experiment to test the effect of a radioactive atmosphere on 

 germination and growth was facilitated by the preparation by Mr. 

 Lieber of a tube lined with the radium coating devised by him. This 

 tube {T, Fig. 5) was connected with the upper tubulure of a glass 

 bell-jar, resting air tight on a ground-glass plate. The lower tubu- 

 lure was connected with an exhaust, so that air, entering the radium- 

 lined cylinder, carried with it into the bell-jar the radioactive emana- 



