COLORS OF NORTH AMERICAN FLOWERS 



currant {Rihes aureum), and of the bush-honeysuckle {Diervilla 

 trifida) in fading change to rose or red. A species of forget-me- 

 not {Myosotis versicolor) is at first yellow, changing later to sky- 

 blue. In the violet family the smallest and simplest species is 

 yellow, and the most highly specialized is blue, while all the 

 intermediate stages are shown by the pansy. 



White Flowers 



White flowers, of which there are 955 species in northeastern 

 North America, are most common in our flora as well as in that 

 of Europe. They contain no pigments, although in some in- 

 stances they contain a white substance, which, when chemically 

 treated, yields a yellow hue. Like the snow and powdered 

 glass, they owe their color to their optical properties — that is, 

 to the reflection and refraction of the rays of light by the minute 

 cells of which they are composed. They are derived from green, 

 yellow, red, and blue-colored ancestors, and are the result of 

 retrogression. In this connection the studies of white leaves 

 by Rodrique, Laurent, and Timpe, which clearly show evidences 

 of degeneration, are of much interest. Such leaves are thinner 

 than normal green leaves, and consist wholly of cellular tissue, 

 the palisade-cells being absent. Whatever impairs the vigor 

 or vitality of the plant, as cold, impoverished soil, injury to the 

 roots, or continued self-fertilization, will cause the floral hues 

 to become paler, or change to white. I once transplanted a 

 scarlet poppy when in bud, and the flowers became much smaller 

 and changed to pure white. ^Miite flowers are most common 

 in the cold days of early spring, and gradually become rarer 

 toward autumn. In the arctic climate of Spitzbergen the 

 flowers are chiefly white, and there are few yellow and red, 

 while blue appears to fail entirely. In east Greenland the 

 flowers are likewise chiefly white, and among 26 species there 



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