134 



EFFECTS OF EXPOSING SEEDS 



The lengths of the hypocotyls above the soil-surface are as follows : 

 December 17, 10 A. M. 



It is seen that the effect produced when the radium-tube is in 

 immediate contact with the seeds is marked, and in agreement with 

 the results of preceding experiments. No effect, however, can be 

 detected when the exposure is made at distances of 20 mm., 40 mm., 

 and 80 mm., and this indicates that the /5 rays are physiologically 

 more effective than the y rays, for, while the former are eliminated 

 by these distances in air, the latter are not, or npt completely. 



