THE CHLOWPLAST PIGMENTS 



469 



in the leaves by capillary attraction, while 

 Tswett thought that the pigment is bound 

 to the framework of the chloroplasts by 

 molecular absorption forces. Willstatter 

 once explained the peculiar behavior of 

 chlorophyll in the leaves toward solvents 

 by the assumption that the chlorophyll 

 probably occurs in the leaf substance in 

 the form of absorption compounds with 

 Colloids. Palladin thought that the 

 chlorophyll is held bound in the leaves in 

 a chemically combined condition with 

 phosphatides. Spectroscopic evidence 

 shows that the absorption bands in the 

 spectrum of living leaves are displaced 

 with respect to the spectrum of a chloro- 

 phyll extract toward the more weakly 

 refracted end. Iwanowski finds that the 

 spectra of leaves and of colloidal chloro- 

 phyll solutions are similar to each other 

 but not identical. He assumes that the 

 chlorophyll is not dissolved in the leaf as 

 a colloid but is present as a fine suspension. 

 Willstatter (1913) believes that the chloro- 

 phyll is present in the leaves in a colloidal 

 state of distribution or in a very similar 

 condition. Zirkle is of the opinion that 

 whatever the union between the chloro- 

 phyll and the ground substance may be, it 

 is not a very strong one, as it can easily be 

 destroyed by many solvents. The union 

 does not seem to affect any of the proper- 

 ties of chlorophyll, while the presence of 

 chlorophyll within the plastid does alter 

 certain properties of the latter. In the 

 first part of this paper the writer has 

 attempted to show that only two carot- 

 inoids are present in the chloroplasts. 



A brief review will now be given of the 

 number of the green pigments. 



Lubimenko inferred from his absorption 

 experiments that there was only one green 

 substance in leaves and that this is broken 

 down by ordinary methods of extraction 

 into chlorophyll a and b and the yellow 

 pigments. Sorby as well as Tswett found 



evidence of three chlorophylls in the 

 brown algae but later Willstatter and 

 Page found no trace of the third component. 

 They found that the chlorophyll of brown 

 algae consisted mostly of chlorophyll a 

 and only traces of chlorophyll b. Wlodek 

 by means of a spectrometer has demon- 

 strated that there are only two chloro- 

 phylls. It is now known that land plants 

 contain about three parts of a to one of 

 b. The history of the two pigments and 

 the difficulties attending their separation 

 need not be related here. It is sufficient to 

 say that it is commonly recognized that 

 there are two and only two green pig- 

 ments present in all green plants. 



THE CHEMICAL INVESTIGATION OF 

 CHLOROPHYLL 



The chemical investigation of chloro- 

 phyll probably began with Berzelius, who 

 first undertook to isolate the green pigment 

 from leaves. He used concentrated acids 

 and alkalies, believing that the pigment 

 was not injured by these chemicals. 



The work of Berzelius undoubtedly had 

 much influence upon later workers as 

 Mulder, Morot, Verdeil and others. To 

 Verdeil we owe our first knowledge 

 regarding the relationship of the coloring 

 matter of blood and of leaves. Chloro- 

 phyll and blood both were considered to 

 contain iron, and this view was main- 

 tained for a long time. Fremy investi- 

 gated the relationship of the green and 

 yellow pigments. Hoppe-Seyler agreed 

 with Verdeil' s ideas regarding blood and 

 chlorophyll and developed further Fremy's 

 lecithin hypothesis of chlorophyll. 

 Hoppe-Seyler later attempted to isolate 

 chlorophyll avoiding energetic reagents. 

 A substance called chlorophyllan was 

 obtained by alcoholic extraction, but this 

 was not chlorophyll at all. Stoklasa even 

 as late as 1907 found potassium and phos- 

 phorus present in chlorophyll. It was 





