Smithsonian Report, 1920 — Garner and Allard. 



Plate 1 5. 



Cosmos. Planted in greenhouse January 5. Plants on left received electric 

 light daily from sunset till midnight, in addition to the sunlight of the day. 

 The artificially lengthened day prevented flowering. Plants on ritrht, 

 which received only sunlight and no artificial illumination, began to flower 

 March 10. Photographed March 23. 



