COLOR 191 



Antliocyan is the most widely distributed 

 coloring substance. It occurs in solution in 

 cell sap, varies from red to blue and violet and 

 may be present in any part of the plant. It 

 may serve as a screen against the disintegrat- 

 ing action of light on chlorophyll and 

 other nitrogenous substances. By its heat- 

 developing power metabolism and transpira- 

 tion may be promoted. 



The coloring matter in marine algae may 

 act as a screen against light and promote 

 metabolism and growth by the development 

 of heat. 



The silvery or white appearance of organs 

 is due to the loose arrangement of the cells. 

 This arrangement serves as a protection 

 against intense sunlight and is found in plants 

 growing in heated deserts. The same arrange- 

 ment may promote transpiration in plants 

 growing in moist shady situations with cool 

 nights or frequent rains. 



The velvety appearance of surfaces is due to 

 the papillose extensions of the outer walls of 

 the epidermis. The extended walls serve as 

 lenses to entrap sunlight and focus it upon 

 the chloroplasts. This adaptation is most 

 useful to plants growing in diffuse light. 



Besides all of the occurrences of pigments 

 noted above, colored substances often are 

 found in the walls of dead cells, as in the 



