60 



MUTATION AND PLANT BREEDING 



The relative penetrations of several different radiations in various 

 kinds of organic materials are indicated in Figure 1 . Penetration into 

 tissue depends upon density of the tissue, but is generally roughly 

 comparable to that shown in Figure 1. 



lOOr 



0.001 



12 3 



Energy, Mev 



Figure 1. — Range and half value thickness (H.V.T.) of various ionizing 

 radiations or particles in (CH 2 ) n . Range or H.V.T. would be roughly 

 the same in plant tissues of similar density. After Sun (182). 



In addition to penetration one should know the pattern of dis- 

 tribution of absorbed energy in the irradiated object (131). The dose 



