COLORS OF NORTH AMERICAN FLOWERS 



Red Flowers 



There are only 257 flowers in the northeastern flora which 

 are described as red; but as there are also 109 red-purple 

 flowers, which should be classed with them, red flowers are thus 

 not so rare as would at first appear. While green and yellow 

 flowers for the most part contain solid-colored granules or 

 plastids, red and blue flowers owe their coloration to a group of 

 pigments dissolved in the cell-sap and called collectively antho- 

 cyanin. Considerable evidence has been obtained that the 

 anthocyanins are derived from the yellow pigments of plants. 

 ^Vhen the anthocyanin salts are acid the flowers are red, when 

 neutral violet, and when alkaline blue; but when the acid salt 

 is neutralized the flowers in some instances become colorless. 

 The color may be again restored by an acid. 



Anthocyanin is very widely distributed among plants, espe- 

 cially among the higher or flowering plants. In early spring the 

 new leaves of many species are suffused with it, as the red 

 maple, the blueberry, and rhubarb; and in autumn it imparts 

 vivid scarlet and crimson hues to the maples, huckleberries, 

 sumacs, and blackberries. It is often abundant on the under- 

 side of floating aquatic leaves and radical leaves growing in 

 rosettes, along stems, and in the root of the beet. It is the 

 prevalent color of the Coleus and purple beech, and it adorns 

 many fruits and berries when ripe. The anthocyanin of foliage 

 is usually red, since the cell-sap of the vegetative organs is, as a 

 rule, acid. 



As the result of many experiments Overton found that the 

 formation of red coloration in plants was influenced by three 

 factors, a cell-sap rich in sugar, intense light, and low tempera- 

 ture. When cut stems of Lilium Martagon and other land- 

 plants were placed in a 2-per-cent invert sugar-solution, red 



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