822 SUMMARY OF CURRENT RESEARCHES RELATING TO 



successive stages of a single flower. For example, one of our common 

 little English forget-me-nots, Myosotis versicolor, is pale yellow when 

 it first opens ; but as it grows older, it becomes faintly pinkish, and 

 ends by being blue, like the others of its race. Now, this sort of 

 colour-change is by no means uncommon ; and in almost all known 

 cases it is always in the same direction, from yellow or white, through 

 pink, orange, or red, to purple or blue. Thus one of the wall-flowers, 

 Gheiranthus chamodeo, has at first a whitish flower, then a citron- 

 yellow, and finally emerges into red or violet. The petals of Stylidium 

 fruticosum are pale yellow to begin with, and afterwards become light 

 rose-coloured. An evening primrose, (Enothera tetraptera, has white 

 flowers in its first stage, and red ones at a later period of develop- 

 ment. Cobcea scandens goes from white to violet ; Hibiscus rnutabilis 

 from white, through flesh-coloured, to red. The common Virginia 

 stock of our gardens (Malcolmia) often opens of a pale yellowish 

 green, then becomes faintly pink, afterwards deepens into bright red, 

 and fades away at last into mauve or blue. Fritz Miiller noticed in 

 South America a Lantana, which is yellow on its first day, orange on 

 the second, and purple on the third. The whole family of Boraginacece 

 begin by being pink, and end by being blue. In all these, and many 

 other cases, the general direction of the changes is the same. They 

 are usually set down as due to varying degrees of oxidation in the 

 pigmentary matter. 



If this be so, there is a good reason why bees should be specially 

 fond of blue, and why blue flowers should be specially adapted for 

 fertilization by their aid; for bees and butterflies are the most highly 

 adapted of all insects to honey-seeking and flower-feeding. They 

 have themselves, on their side, undergone the largest amount of 

 specialization for that particular function. And if the more specialized 

 and modified flowers, which gradually fitted their forms and the posi- 

 tion of their honey-glands to the forms of the bees or butterflies, 

 showed a natural tendency to pass from yellow, through pink and red, 

 to purple and blue, it would follow that the insects which were being 

 evolved, side by side with them, and which were aiding at the same 

 time in their evolution, would grow to recognize these developed 

 colours as the visible symbols of those flowers from which they could 

 obtain the largest amount of honey with the least possible trouble. 

 Thus it would finally result that the ordinary unspecialized flowers, 

 which depended upon small insect riff-raff, would be mostly left yellow 

 or white ; those which appealed to rather higher insects would become 

 pink or red ; and those which laid themselves out for bees and butter- 

 flies would grow for the most part to be purple or blue. Now, this is 

 very much what we actually find to be the case in nature. 



Causes of the Etiolation of Plants.* — E. Mer points out that 

 the aquatic forms of amphibious plants present, in their external 

 appearance and internal structure, a close analogy with the forms of 

 aerial plants grown in the dark or in moist air. A comparison of 

 these phenomena shows that etiolation is the result of a variety of 



* Comptes Eendus, xcv. (1882) pp. 487-9. 



