FOREWORD 



Twentieth century man is managing plant growth 

 with success undreamed of by farmers and gardeners 

 before him. But scientists who explore plant life are 

 aware that far greater success is ahead --when they 

 can explain precisely how and why plants grow as 

 they do on a sunlit earth. 



Major progress toward this goal comes through 

 discoveries disclosing the sun-operated clockwork in 

 plants that controls each change in the life cycle from 

 seed germination to fruiting. 



Agricultural leaders will increasingly need infor- 

 nnation on this light-growth research and its implica- 

 tions, as background for appraising and explaining 

 many of the new developments in plant science. 



Information in this report was provided by the Crops Research Division 

 and the Soil and Water Conservation Research Division of the Agricultural 

 Research Service. 



