SELECTIVE SCATTERING OF LICJIIT 



103 



mitt'ed light of longer wavelengths (sharp cut-off red filter), and 

 another which transmitted mainly light of shorter wavelengths (in- 

 frared-absorbing blue filter). Polaroid plates were used in the second 

 method (described b}^ Brice, Nutting, and Hawler (1)). 



Corrections found in all three ways were in excellent agreement 

 everywhere except at 680 to 700 m/x, where the different methods led 

 to corrected scattering curves which deviated by up to 10% from the 

 average ones shown in the figures. 



X 



— • SCATTERING 

 .— ABSORPTION 



400 450 500 550 600 650 



WAVE LENGTH (m>i) 



700 



750 



Fig. 4. Scattering and absorption of the blue-green alga Synechocysiis. 



Investigations of crystalHne chlorophyll by Jacobs (2) and of 

 suspensions of colloidal chlorophyll by one of the authors had re- 

 \-ealed that these systems scatter light with a spectral selecti-\-ity 

 similar to that shown in our (;urves for algal, cells. 



The light scattered by the cells originates from two sources: 

 (/ ) colorless structures, which scatter with a relatively uniform wave- 

 length dependence (not unlike the scattering by bleached cells, shown 

 in Fig. 2), and (2) highly pigmented chloroplasts (or grana), which 

 scatter light with a strong spectral selectivity. The (juantitative in- 

 terpretation of the scattering by pigmented cellular components re- 

 quires a rather complex theory, such as that of Mie (3). Qualitati\-ely, 

 the capacity to scatter light should increase sharply with the index 



