108 PHOTOSYNTHESIS 



tools he is using. The great industrial development in illumination during 

 recent years and the wealth of exact physical information which has ac- 

 companied it has made available tremendously valuable facilities for 

 experimental work in this field. There are also a number of authentic 

 compilations of data in book form relative to these matters. ^^ 



In Table 20 is given the relative distribution of energy in the visible 

 spectra of a number of common sources of light with wave-length 0.59 [i 

 equal to 100. It is evident from this that differences in photosynthesis 

 are to be expected when different sources of light are employed. 



TABLE 20 



Relative Distribution of Energy in the Visible Spectra of Different Sources 

 OF Light. (From Luckiesh, "Color and Its Application." 1921.) 



Tungsten Tungsten 



Incandescent Incandescent 



Lamp Lamp 



The first to observe a difference in photosynthetic activity in light of 

 different color was Senebier.'" This Swiss scientist devised the double 

 walled bell jars, capable of being filled with solutions of different color, 

 which have found extensive use in plant-physiology. Senebier found that 

 plants growing under identical conditions under white, red, and blue light 

 formed most oxygen in the white, next in the red, and least in the blue 



"Sheppard, S. E., Photochcniistry. Longmans, Green Co., 1914. Plotnikow, J., 

 Photochcmische Vcrsuchstcchnik. Leipzig, 1912. Idem., Allgemeine Photochemie. 

 Berlin and Leipzig, 1920. Luckiesh, M., Ultraviolet Radiation. Van Nostrand 

 Co., 1922. Idem., Artificial Light. Its Influence Upon Ciznli:;ation, 1920. Idem., 

 Color and Its Application, 1921. Ellis and Wells, The Chemical Action of Ultra- 

 violet Rays. Chemical Catalog Co., 1925. Hiibl, A., Die Lichtfllter. Halle, 1921. 



" Senebier, Jean, "Memoires physico-chimiques sur I'influence de la lumiere solaire 

 pour modifier les etres des trois regncs de la nature et surtout ccux du regne 

 vegetale," Geneve, 1782. German translation by F. H. Jacobaer, Leipzig, 1785, Vol. 

 I, p. 153. 



