THE PHOTOTROPHIC ASSIMILATION OF CARBON 19 



ment of photosynthesis is to be found in a number of 

 recent pubUcations.^^^ 248, loo, so, 99, 113, 261 



THE ALGAL PIGMENTS AND THE UTILIZATION OF LIGHT 



IN PHOTOSYNTHESIS 



Three principal types of pigment are to be found in algae. 

 These are the chlorophylls, the carotenoids and the phyco- 

 bilins. The chlorophylls are characterized by possessing a 

 cyclic tetrapyrrolic nucleus containing magnesium. They 

 are soluble in fat solvents giving fluorescent solutions 

 having pronounced absorption bands in the blue or blue- 

 green and in the red or infra-red (Fig. 3). Carotenoid pig- 

 ments are likewise soluble in fat solvents but have a yellow 

 or orange colour resulting from absorption in the blue and 

 the green (Fig. 3). Carotenoids generally contain about 



0-S 



400 440 480 520 560 600 640 660 

 mVE LENGTH IN MjU 



FIG. 3. Absorption spectra of methanol solutions of pigrnents 

 extracted quantitatively from cells of Navicula minima (after 

 ref. 280). 



