CONCENTEATION OF CHLOROPHYLL IN LEAVES 407 



with any one of the numerous transformation and decomposition products 

 of chlorophyll a which can be separated by chromatographic methods. 



The same pigment also was found by Strain, Manning, and Hardin 

 (1943) in a dinoflagellate {Peridinium cinctum). Strain and Manning 

 concluded that chlorofucin is a normal component of at least three major 

 classes of algae {Phaeophyceae, Diatomeae, Flagellatae) and perhaps serves 

 as a substitute for chlorophyll b. The proportion of "chlorophyll c" 

 has not been determined, but it appears from the published absorption 

 curves that it cannot exceed 10% of the total quantity of chlorophyll. 



Chlorophyll c is not found in red algae, which contain, however, 

 according to Manning and Strain (1943), still another pigment, a "chloro- 

 phyll d," characterized by an absorption band far in the red, at 696 mju 

 (in methanol). An isomeric form, d', of this pigment also was found. * 



4. Bacteriochlorophyll and Bacterioviridin 



The green pigments of sulfur bacteria, bacterioviridin and bacterio- 

 chlorophyll, are close relatives of the chlorophylls of the higher plants 

 and algae. Bacterioviridin is as yet almost unknown; but bacterio- 

 chlorophyll has been much studied recently. Fischer and coworkers 

 (of. Fischer 1940) found only one component of this pigment whose 

 chemical structure makes it an analogue of chlorophyll a. Seybold and 

 Egle (1939) found three components in the chromatograms of extracts 

 from Thiocystis — a steel-blue "bacteriochlorophyll a," a, green "bacterio- 

 chlorophyll 6" and a "bacteriochlorophyll c" — but held it possible that 

 the "b" and "c" components were secondary products, formed while 

 the pigment was allowed to stand for several hours in methanol solution. 



5. Concentration of Chlorophyll in Leaves 



The concentration of chlorophyll in leaves and algae can be referred 

 to fresh weight, dry weight, cell volume, or surface. None of these 

 methods is entirely satisfactory. Reference to unit surface, favored in 

 many studies of the leaves of the higher plants, and suitable when a 

 measure of their color density is desired, is inappropriate for algae, 

 especially the unicellular ones. Reference to unit fresh weight, or cell 

 volume, may be deceiving in the case of plants with an abnormally large 

 water content (compare Fig. 48). For plant organs containing a large 

 proportion of colorless tissue, e. g., the fleshy leaves of the succulents, the 

 reference to either fresh or dry weight may give deceivingly low figures. 



The first determinations of chlorophylls a and 6 in a large number of 

 higher plants were carried out by Willstatter and Stoll (1913, 1918); 

 a second extensive study was made by Seybold and Egle (1937, 1938, 



* Further details of these new results will be found in Vol. II, Chap. 21. 



