156 THE CHEMISTRY OF THE PLANT 
Phycocyanin 
Phycophaein 
Diatomin 
Phycoerythrin 
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, ete. 
Other plant pigments, of un- 
known composition, may be 
associated with the two pre- 
ceding pigments, giving char- 
atceristic 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. 
In the Myxophyceae, blue, 
water soluble. 
In the Phaeophyceae, brown. 
In Bacillarioideae (diatoms) 
brown, water soluble. 
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 leaves and other plant 
parts, occurring especially in 
the epidermal cells. It is ap- 
parently a nitrogen-free glu- 
coside, 
