52 PLANT PHYSIOLOGY 



The chief physical characteristics of chlorophyll, which is 

 probably made as well as contained in the chromatophores, 

 are its complete insolubility in water, its ready solubility 

 in alcohol, its fluorescence, and the absorption bands of its 

 spectrum. By reason of its insolubility in water, it is pos- 

 sible to separate chlorophyll from the other pigments some- 

 times masking its presence in the cell — the blue of the ScM- 

 zopbycesc, the brown of the Phseophycesp, the red of the 

 Cnvpophyceae, and the red and purple coloring-matters 

 often present in the cell-sap of higher plants. * Having ex- 

 tracted these pigments in cold water, alcohol may be used 

 to dissolve the chlorophyll, which wiU certainly go into 

 solution more rapidlj', and possibly also with less chemical 

 change, if the alcohol be applied hot. Besides the chloro- 

 phyll, this extract will contain other cell-contents soluble in 

 alcohol and not removed by the water, notably the fats and 

 oils. The alcoholic solution is ordinarily very unstable, for 

 though it wiU retain its color for a few days if kept in 

 the dark, the change in color, which begins at once, continu- 

 ing only less rapidly than in the light, is evidence of chem- 

 ical changes finally resulting in its complete destruction. 

 From a freshly made alcoholic extract of chlorophyll at 

 least two colored substances may be separated in solution. 

 Benzine or gasoline shaken with an equal volume of the 

 alcoholic extract will take up the chlorophyU-green proper, 

 leaving a yellow pigment or pigments in solution in the 

 alcohol. This will not secure a complete separation of the 

 two, however, for some of the yellow pigment will remain in 

 the benzine. This yellow pigment is usually called carotin. 

 To separate chlorophyll-green in anything approaching 

 purity is a diflicult task. The extreme instability of the pig- 

 ments enclosed in the chromatophores makes it almost cer- 

 tain that they wiU be acted on by the organic acids present 

 in the cells and extracted with them. Furthermore, the 

 solvents of chlorophyll ( alcohol, ether, etc. ) extract the 

 fats and oils also. Although many attempts have been 



* Molisch, H. Das Phycoerythrin, seine Krystallisirbarkeit und chem- 

 ische Natur. Bot. Zeitung, Bd. 52, 1894. Das Phycocyan, ein krystal- 

 lislrbarer Eiweisskorper. Ibid.. Bd. 54, 1895. 



