74 



MUTATION AND PLANT BREEDING 



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DISTANCE IN MICRONS FROM SOURCE 

 Figure 5. — Radiation doses about a point source of tritium. After Rob- 

 ertson and Hughes (129). 



2. Chromosome, chromatid or subchromatid aberrations 



The type of aberration produced depends upon the number of 

 strands present in the chromosome, on the length or density of the 



