2 24 THE POPULAR SCIENCE MONTHLY 



environment, and plant physiology and the newer physics join hands. 

 Here, as elsewhere, the boundaries between the different " sciences " 

 break down. 



Fig. 1 is from a photograph of a few of the preparations employed 

 in the experiments about to be described. The three marked R are 

 sealed glass tubes containing radium bromide. The figures indicate 

 the degree of activity of the preparations in terms of the activity of 

 uranium taken as a unit. Eadium bromide of 1,800,000 activity is the 

 purest salt thus far obtained. The lower right-hand tube contains 

 radio-tellurium, which gives off only a rays. 



The rod below the tubes is of celluloid, coated on one end with 

 radium bromide of 25,000 activity. The radium coating is overlaid 

 with one of celloidin for purposes of protection. 



By means of the rod, not only the three kinds of rays, but the 

 emanation as well, are available. The walls of the sealed glass tubes 

 permit the ft and y rays to pass, but the emanation and the a rays' 

 not at all. 



Eadium coatings, such as those on the rod, were devised by Mr. 

 Hugo Lieber, of New York City, and are a valuable aid in studying 

 the physiological role of radium. The experiments of the writer, car- 

 ried on for over three years at the New York Botanical Garden, were 

 made possible solely through the great liberality of Mr. Lieber, who 

 freely supplied all the standard preparations, several thousand dollars 

 worth in all. 



In none of the experiments did the radium itself come in contact 

 with the plant tissues. The results noted were due to the action of 

 the rays alone. When the sealed glass tubes were used, the effect was 

 produced by the /? and 7 rays, acting together; when the radium coat- 

 ings were employed, by the combined action of the emanation and the 

 rays, a, ^ and 7. 



To review the results obtained by other investigators is beyond the 

 scope and purpose of the present article. Koernicke, Dixon and 

 Wighman, A. B. Greene, Guilleminot and Abbe, not to mention others, 

 have experimented on the action of radium rays on germination and 

 growth, and, to a slight extent, u.pon other plant processes. There 

 seems to be general agreement among them that the rays exert a 

 retarding or an inhibiting effect, depending upon the activity of the 

 preparation employed and the duration of exposure to the rays. 



Germination is easily retarded or inhibited by exposing seeds while 

 dry, or during imbibition of water. In one experiment ten seeds of 

 " Lincoln " oats, after being soaked in water overnight, were exposed 

 for eighteen hours to rays from the tube of 10,000 activity, by being 

 placed with their embryo-sides in contact with the tube. Germination 

 was retarded by this treatment. After being exposed for about 50 

 hours longer to the same preparation (67 hrs. 35 min. in all), the 



