158 VEGETABLE PHYSIOLOGY 



chlorophyll by alcohol. It can be separated from the 

 extract by appropriate means, and its solution yields the 

 absorption spectrum represented below those of chlorophyll 

 in fig. 86. Another pigment, Erythrophyll, is present in 

 those leaves which are found upon the trees in autumn. 

 Like xanthophyll, it appears to be a product of the decom- 

 position of chlorophyll, and it has a spectrum which differs 

 from both the others. 



It is extremely difficult to say what is the chemical 

 composition of chlorophyll, on account of the readiness with 

 which it is decomposed. In all the processes which have 

 been adopted for its extraction it undergoes decomposition, 

 and consequently no definite conclusions as to its chemical 

 nature can at present be arrived at. It can be made to 

 yield definite crystals by appropriate methods of treatment 

 after extraction, but it is probable that these crystals are 

 a derivative of chlorophyll and not the pure pigment. 

 Analyses of the crystals have been made by Gautier and by 

 Hoppe-Seyler, who give them the following percentage 

 compositions : 



Gautier Hoppe-Seyler 



C 73-97 73-34 



H 9-8 9-72 



N 4-15 5-68 



10-33 9-54 



Ash 1-75 1-72 



According to Hoppe-Seyler the ash contains phosphorus 

 and magnesium. 



From his analysis Gautier came to the conclusion 

 that chlorophyll is related to the colouring matter of the 

 bile ; Hoppe-Seyler considered, on the other hand, that it 

 is a fatty body allied to lecithin. 



Except in the lowest unicellular plants, the chlorophyll 

 is always attached to some form of protoplasmic body 

 known as a plastid. These are small masses, of varying 

 size and shape, which are embedded in the general cyto- 



