No. 504] PHYSIOLOGICAL EFFECTS OF RADIUM BATS 705 



at the end of three days (70 hours) the radicles of the 

 exposed seeds averaged 3.81 mm. in length, those of the 

 control set 21.80 mm. The retardation of germination 

 and growth following this treatment is illustrated in 

 Fig. 1. 



A row of timothy grass seed (Phleum pratense) was 

 sown on a moist blotter. Over the center of the row was 

 suspended vertically a sealed glass tube containing 10 mg. 

 of radium of 1,500,000 activity in the end of the tube 

 nearest the seeds. The distance from the tube to the 

 seeds was about 5 mm. A second row was also arranged 

 as a control (not exposed to radium). At the end of 

 eleven days the control seedlings were all of about the 

 same height and color (normally green) and averaged 

 30 mm. in height. The exposed plants were entirely 

 etiolated directly under the radium tube and for a 

 radius of 4 mm. on each side. The height of the seed- 

 lings gradually decreased from 30 mm. (average) at the 



ends of the row, to 3 mm. at the center under the radium 

 (Fig. 2). 



Twenty seeds of "Lincoln" oats (Avena), with the 

 glumes removed, were placed in two parallel rows with 

 the radicle ends touching, and the embryo-side upper- 

 most. Over them was laid the sealed glass tube of 

 radium bromide of 1,500,000 activity, resting on the 

 radicle ends of the seeds. After an exposure of 6 days 



