3IO THE CHLOROPHYLLS AND THE CAROTINOIDS 



light are much more completely absorbed than others. The regions of the 

 spectrum in which complete or nearly complete absorption takes place appear 

 as dark bands. Each of the two chlorophylls shows a definite and character- 

 istic absorption spectrum when in solution. The exact appearance of such 

 absorption spectra will vary, however, depending upon the concentration and 

 the thickness of the layer of solution which is examined. Absorption curves for 

 chlorophyll a and chlorophyll b in ether solution as determined by photo- 



500 600 700 



WAVE LENGTHS IN MILLIMICRONS 



800 



Fig. 8 1. Absorption spectra of chlorophylls a and h in ether solution. Data of 



Zscheile (1934). 



electric measurements are shown in Fig. 81. Both chlorophylls exhibit maxi- 

 mum absorption in the blue-violet region and a secondary maximum in the 

 short red. 



Physicochemical State of Chlorophyll in the Chloroplasts. — Although 

 the extensive investigations of the physical and chemical properties of chloro- 

 phyll extracts have advanced our knowledge of chlorophyll in certain direc- 

 tions, it should be remembered that these are only extracts and tell us nothing 



