LATE ORIGIN OF BLUE FLOWERS. 309 



varieties are whitish-yellow; the larger and more 

 highly developed, blue. Myosoiis versicolor we know 

 is first yellow and then blue ; and, according to Miiller, 

 one variety of Y. tricolor alpestris is yellow when it 

 first opens, and gradually becomes more and more blue. 

 In this case the individual flower repeats the phases 

 which in past times the ancestors have passed through. 



The flowers of one species of Lantana last three 

 days, and, as Fritz Miiller first pointed out, are on the 

 first day yellow, on the second day orange, and on the 

 third day purple. 



The only other family I will mention is that of the 

 Gentians. Here, also, while the well-known deep blue 

 species have long tubular flowers, specially adapted tc 

 bees and butterflies, the yellow Gentiana lutea has 

 a simple open flower with exposed honey. 



Miiller and Hildebrand ' have also pointed out that the 

 blue flowers, which, according to this view, are descended 

 from white or yellow ancestors, passing in many cases 

 through a red stage, frequently vary, as if the colours had 

 not had time to fix themselves, and by atavism assume 

 their original colour. Thus Aqidlegia vulgaris, Ajuga 

 Genevensis, Poly gala vulgaris, P. comosa. Salvia pra- 

 tensiSf Myosoiis alpestris, and many other blue flowers, 

 are often reddish or white ; Viola calcarata is normally 

 blue, but occasionally yellow. On the other hand, flowers 

 which are normally white or yellow, rarely, I might 

 almost say never, vary to blue. Moreover, though it is 



* Die Farben der BlUthen, p. 26. 



