sparrow: cytogenetic effects of ionizing radiations 105 



mutagens and of various techniques of exposure are urgently needed. 

 In spite of rapid progress being made, our knowledge of radiobiology 

 and radiation genetics leaves much to be desired with respect to our 

 ability to define or predict the most efficient methods for the produc- 

 tion of useful mutations in plants. Expansion of the research effort 

 at both basic and applied levels is desirable. 



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