148 



VEGETABLE PHYSIOLOGY 



chlorophyll absorbs these particular rays of light which are 

 missing. 



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 spec- 

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



W V M 



FIG. 84. ABSORPTION SPECTRA OF CHLOROPHYLL AND 

 XAKTHOPHYLL. (After Kraus.) 



T2f 



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 

 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 prominent. 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 decom- 



