LA W OF PROGRESSIVE COLOURA TION. 59 



among Dicotyledons, and may therefore best be con- 

 sidered in the succeeding chapter. 



This brief review of the chief families of English 

 entomophilous flowers will probably have made clear 

 the general truth of the law of progressive coloura- 

 tion here laid down. There are many exceptions and 

 special peculiarities, some of which will be explained 



FIG 22. Flower of common flag (Irisfcetidisshna) ; violet blue. 



or accounted for in the sequel ; but on the whole we 

 may consider the following facts fairly proved : 



(i.) Most of the very simplest flowers are yellow. 

 (2.) Many of the simpler flowers in each family 



(except the highest) are apt to be yellow. 

 (3.) The more advanced members of very simple 

 families are usually white or pink. 



