418 



THE PIGMENT SYSTEM 



CHAP. 15 



Despite the solubility of the chromoproteids in water, which makes 

 their extraction easy (it is sufficient to kill the cells, chemically or me- 

 chanically, and allow the pigment to diffuse into distilled water), their 

 purification and separation involves considerable difficulties; and only 

 few data exist as to their absolute concentration in the algae. According 

 to Lemberg (1928), the red alga, Ceramium ruhrum, in winter, contains 

 1.9% of pigment (relative to dry weight), one-fourth of which is phyco- 

 erythrin. In summer, the content of pigment is 0.9%, with one-third 

 phycoerythrin. Kylin (1910) calculated, for the same species, 0.67% 

 phycoerythrin in April (relative to dry weight after subtraction of ash) 

 and 1.5% in March. Lubimenko (1925) gives the figures in table 15. VII 

 for the ratio of [phycoerythrin]: [chlorophyll] for red algae of different 



origin. 



Table 15.VII 

 Phycoerythrin-Chlorophyll Ratio (after Lubimenko) 



Lubimenko classified all algae in six groups, with ratios 0.06, 0.12, 0.24, 0.36, 0.42 

 and 0.66, respectively (Table 15.VII), and stressed the gradual increase in relative 

 proportion of the red pigment with increasing depth of the habitat (c/. page 421). 



All these determinations indicated that the concentration of the red 

 pigment is of the same order of magnitude as, or even smaller than, 

 that of chlorophyll. According to Lemberg (1928), the chromophore 

 constitutes only 2% by weight of the chromoproteid. Thus, a mass 

 ratio of 1 : 1 of chlorophyll and phycoerythrin corresponds to a molecular 

 ratio of about 50 : 1 (assuming that the molecular weight of the chromo- 

 phores are equal). This predominance of the green pigment seems to be 



