156 



THE CHEMISTRY OF THE PLANT 



ing the characteristic "grass 

 green" color to the chloro- 

 plasts. It is present without 

 chlorophyll in autumn leaves 

 and in many parts of some 

 plants. The autumn colora- 

 tion of leaves is due to various 

 chemical changes of carotin 

 and chlorophyll and other sub- 

 stances present in the cells. 

 Carotin is of itself yellow to 

 orange when in solution, form- 

 ing orange-red to red crystals. 

 It is insoluble in water, petrol- 

 eum ether and gasoline, but 

 soluble in alcohol, ether, etc. 

 Other plant pigments, of un- 

 known composition, may be 

 associated with the two pre- 

 ceding pigments, giving char- 

 acteristic colors to the chloro- 

 plasts. Their function is not 

 proved, but in some cases they 

 probably change the quality of 

 light to that most favorable for 

 absorption by the chlorophyll. 



Phycocyanin In the Myxophyceae, blue, 



water soluble. 



Phycophaein In the Phaeophyceae, brown. 



Diatomin In Bacillarioideae (diatoms) 



brown, water soluble. 



Phycoerythrin In Rhodophyceae and a few 



Siphonophyceae, violet-red, 

 water soluble. 



Anthocyanin is a red (in acid cell sap) or blue (in alkaline cell 



sap) coloring matter in the 

 cell sap of many brightly 

 colored loaves and other plant 

 parts, occurring especially in 

 the epidermal cells. It is ap- 

 parently a nitrogen-free glu- 

 coside. 



