186 Plant-Breeding 



1. White is due to the absence of pigment, and to the 

 reflection of light from the cells. 



2. Green color is caused by the presence of a green 

 pigment in the chlorophyll. 



3. Yellow, cream, and related colors are due to a 

 yellow pigment either associated with green in the chloro- 

 plasts or found alone in the chromoplasts, generally the 

 latter. Yellow may sometimes come from the cell-sap. 



4. Red color may, under certain circumstances, be due 

 to the presence of that pigment in the chromoplasts, but 

 it is ordinarily a cell-sap color. 



5. Most of the remaining colors, purple, blue, generally 

 red, pink, etc., are due to pigments in the cell-sap. 



6. Many of the colors and shades found in flowers 

 are the result of both plastid colors and cell-sap colors 

 acting together in various amounts. 



7. Certain of the denser plastids or cell-sap colors may 

 cover up the more delicate colors so that they cannot be 

 seen. 



8. Finally, the color in the cell-sap may be due to 

 the relative presence of a non-nitrogenous and chemical 

 substance anthocyanin. This is blue in an alkaline and red 

 in acid reacting cell-sap, and, under certain conditions, 

 also dark red, violet, dark blue, and even blackish blue. 

 Anthocyanin can be obtained from the supersaturated 

 cell-sap of a number of deeply colored parts of plants in 

 a crystalline or amorphous form. Blood-colored leaves, 

 such as those of the Copper Beach, owe their characteris- 

 tic appearance to the united presence of green chlorophyll 

 and anthocyanin. The different colors of flowers are due 

 to the varying color of the cell-sap, to the different dis- 



