l6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 97 



tions of the plants for good growth were such that from 14 to 51 

 percent of the total radiation falling on them came from the mercury 

 lamp. In several cases better growth was attained in one mixture of 

 wave-lengths than in another where the total intensity was higher. 

 However, the relatively high growth efficiency may in part be due to 

 an intermittency effect occurring in gaseous discharge tubes such as 

 the mercury lamp here used. 



LITERATURE CITED 



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1935. Relative growth and dry weight production of plant tissue under 

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