Smithsonian Report. 1936. — Johnston 



PLATE 2 



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Courtesy R. B. Withrow. 



1. Effect of supplementary artificial illumination on forcing aster (Heart of France) into flowering. 



Courtesy R. B. Withrow. 



2. Wave-length effects of supplementary artificial illumination on a long-day plant (stock). 



Courtesy R. B. Withrow. 



3. Wave-length etTects of supplementary artificial illumination on a short-day plant (salvia). 



