26 



PHYSIOLOGY OF NUTRITION. 



The bine-green cyanophyll has seven absorption bands I. in the 

 red, II. in the orange, III. in the yellow, IV. in the green, V., 

 VI. and VII. in the blue and violet. 



When we observe concentrated solutions of chlorophyll by 

 reflected light, they are seen to have a red colour. The red colour 



100 



100 



FIG. 8. Absorption spectra of chlorophyll after Kraus. The uppermost spectrum is 

 that of the alcoholic extract of green leaves, the middle one that of the blue-green con- 

 stituent dissolved in benzol, the lowest one that of the yellow constituent. The absorption 

 bands of the two upper spectra are given, in the less refrangible parts B-E, as from a more 

 concentrated solution, in the more refrangible portions as from a dilute solution. The 

 letters A-G indicate the position of the well-known Frauenhofer's lines of the sun's 

 spectrum ; the numbers I.-VII. denote, after Kraus, the absorption bands, proceeding from 

 the red to the violet. The divisions 0-100 subdivide the spectrum into 100 equal parts. 



of the solution of chlorophyll by reflected light is shown still 

 more distinctly and beautifully when we throw a beam of light 

 on the surface of the solution by means of a biconvex lens. 

 Chlorophyll fluoresces with red light, as can thus easily be 

 determined. 



1 See Kraus, Zur Kenntniss der Chlorophyll farbstoffe, 1872 ;. Pringslieim, 

 Monatsber. d. Berliner Akademie, 1874 and 1875, and Sitzimysber. ch Berliner 

 Akademie, 1886 ; Hanseii, Arbeiten d. botan. Institute in Wiirzburg, Bd. 3, H. 1 ; 

 Tschirch, Berichte d. Deutschen botan. Gesellschaft, Bd. 1. 



