26o PIGMENTS 



of plants, no matter what their composition may be, phyto- 

 haematins. 



It does not follow that all definite coloured compounds 

 are formed during respiration ; it all depends on the relative 

 activities of the oxidases and the reductases. A pigment will 

 make its appearance provided the oxidases are the more 

 potent, but if the reductases are the more active no pigment 

 will appear. 



The method of indicating the presence of a chromogen is 

 obvious ; the material to be examined is extracted and heated 

 to a degree of temperature sufficient to destroy any enzymes 

 present. To this preparation is added peroxidase and hydrogen 

 peroxide ; if a chromogen were present originally, then a 

 coloration will result, usually brown, red, or purple. 



