PIGMENTS 



155 



Suberin 



Cutin 



Chlorophyll (chlorophyllan) 



Carotin (Xanthophyll) 



C26H3a 



This is the name appUed to 

 what is probably a mixture of 

 several fatty acids including 

 the following : PheUonic, phloe- 

 onic and suberic (CsHuOs). 

 Their presence in the ceU walls 

 waterproofs them. 

 This is a fatty substance or 

 substances related to the fore- 

 going and waterproofing the 

 epidermal cell walls in which 

 it is deposited. 



This is a blue-green pigment 

 occurring only in chloroplasts 

 (or in such Myxophyceae as 

 lack definite chloroplasts in 

 minute particles in the cyto- 

 plasm). It is the most im- 

 portant plant pigment, ab- 

 sorbing certain light rays and 

 transforming the energy into 

 the chemical energy used in 

 photosynthesis. It is formed 

 (with rare exceptions) only in 

 the light and is itself quickly 

 destroyed by bright Hght. It 

 contains no iron but the plant 

 requires iron for its produc- 

 tion. Its chemical composi- 

 tion is not exactly known but 

 it seems to be closely related 

 to haemoglobin. It is insoluble 

 in water but soluble in alcohol, 

 ether, petroleum ether, gaso- 

 line, etc. Probably "chloro- 

 phyll" is not one but a group 

 of closely similar compounds. 

 Under the name Xanthophyll 

 this substance is associated in 

 small or large proportions 

 with chlorophyll wherever the 

 latter occurs, the mixture giv- 



