THE CHLOROPHYLL APPARATUS 



143 



In fig. 84 is a representation of the spectrum which 

 such treatment produces and which is called, from the facts 

 just narrated, the absorption spectrum of chlorophyll. The 

 uppermost figure is that which is exhibited by an alcoholic 

 solution or extract of leaves ; the middle one is given by 

 chlorophyll dissolved in benzol. The first band on the left 

 is the darkest, and is found to be in the red part of the 

 spectrum. The three bands on the right are broader, but 

 are not so well defined. They cover nearly all the blue end. 

 The three thinner and lighter bands are in the yellow and 

 green parts of the spectrum. Chlorophyll therefore has 



120 30 149 50! 



LLLf Lull i I 



FIG. 84. ABSORPTION SPECTRA OF CHLOROPHYLL AND 

 XANTHOPHYLL. (After Kraus.) 



the power of absorbing a large number of red rays, a good 

 many blue and violet ones, and a few of the green and 

 yellow. The distinctness with which these absorption 

 bands are seen depends upon the strength of the solution, 

 those in the red and blue being, however, always promi- 

 nent. Careful experiments have proved that chlorophyll 

 is a single pigment and not a mixture of two, as has often 

 been stated. It is, however, easily decomposed, and the 

 products of its decomposition are generally found with it 

 in the chloroplast. One of these, Xanthophyll, which is 

 of a bright yellow colour, is always extracted with the 



