THE COLORS OF FLOWEHS. 201 



appearance, and yet mutually infertile, it is easy to 

 see that it would be an advantage to them to have 

 their flowers diflerently colored. The three species 

 of Lamium above mentioned may be growing together, 

 and yet the bees, without difficulty or loss of time, can 

 distinguish the species from one another, and collect 

 pollen and honey without confusing them together. On 

 the other hand, if they were similarly colored, the 

 bees could only distinguish them with comparative 

 difficulty, involving some loss of time and probably 

 many mistakes. 



I have not yet alluded especially to white flowers. 

 They seem to stand in a somewhat special position. 

 The general sequence, as I have suggested, is from 

 green, through yellow and red, to blue. Flowers 

 normally yellow seldom sport into red or blue ; those 

 normally red often sport into yellow, but seldom into 

 blue. On the other hand, flowers of almost any color 

 may sport into white. White is produced by the 

 absence of color, may therefore appear at any stage, 

 and will be stereotyped if for any reason it should prove 

 to be an advantage.* 



* The genesis of the color is a large and interesting question. It 

 may be due to various causes, and is by no means always owing to the 

 presence of a diflerent coloring matter. For instance, as Professor 

 Foster has observed to me, many species of Iris occur in blue and 

 yellow forms. The yellow is largely, or wholly, produced by chroma- 

 toplacts, the purple or blue to cell-sap, and if the latter is absent the 

 yellow becomes apparent. 



