CHAPTER VIII 

 PIGMENTS 



PRACTICALLY all plant structures contain pigments. These may 

 be considered as of two types: (a) the vegetative pigments, which 

 have a definite energy-absorbing role in the metabolic processes 

 of the tissues which contain them, and (6) the ornamental pig- 

 ments. It is probable that the same chemical compound may 

 serve in either one of these capacities under different conditions, 

 but, in general, it is possible to assign either a definite vegetative, 

 or physiological, use, or else a simple ornamental, or biological, 

 significance to each of the common pigments. The first type is 

 found widely distributed through the protoplasm, or cell-sap, 

 of the plant structures ; while the ornamental pigments are located 

 chiefly in the epidermal cells, especially of flowers. 



With respect to their colors, the plant pigments may be 

 grouped as follows: 



Green the chlorophylls. 



Yellow the carotinoids, flavones, and xanthones. 



Red phycoerythrin, lycopersicin, anthocyanin. 



Blue anthocyan derivatives. 



Brown phycophaein, fucoxanthin. 



Of these, the chlorophylls, the carotinoids, phycoerythrin (in 

 red sea-weeds) and phycophaein (in brown sea-weeds) are gener- 

 ally vegetative pigments; while the others form the basis for most 

 of the ornamental pigments, although they may have a definite 

 energy-absorbing effect, in some cases. 



THE CHLOROPHYLLS 



The importance of the green coloring matter in plants has 

 been understood for more than a century, its connection with 



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