200 THE COLOES OF FLOWERS. 



have descended from ancestors in which the flowers 

 were red, these from others in which they were yellow, 

 while originally they were all green — or, to speak more 

 precisely, in which the leaves immediately surrounding 

 the stamens and pistil were green ; that they have 

 passed through stages of yellow, and generally if not 

 always red, before becoming blue. 



It is, of course, easy to see that the possession of color 

 is an advantage to flowers in rendering them more 

 conspicuous, more easily seen, and less readily over- 

 looked, by the insects which fertilize them ; but it is 

 not quite so clear why, apart from brilliancy and 

 visibility at a distance, one color should be more 

 advantageous than another. These experiments how- 

 ever, which show that insects have their preference, 

 throw some light on the subject. 



Where insects are beguiled into visits, as is the case 

 especially with flies, they are obviously more likely to 

 be deceived if the flowers not only, as is often the case, 

 smell like decaying animal substance, but almost re- 

 semble them in appearance. Hence many fly flowers 

 not only emit a most offensive smell, but also are dingy 

 yellow or red, often mottled, and very closely resemble 

 in color decaying meat. 



There remains another case in which allied flowers, 

 and species, moreover, which are fertilized by very much 

 the same insects, are yet characterized by distinct 

 colors. We have, for instance, three nearly allied 

 species of dead nettle — one white (Lamium alhum), one 

 red {Lamium maculatum), and one yellow {Lamium 

 galedhdolon or luteum). 



Now, if we imagine the existence in a single genus 

 of three separate species, similar in general habit and 



