22 THE COL O URS OF FL WERS. 



violet ; Hibiscus miitabilis from white, through flesh- 

 coloured, to red. The common Virginia stock of our 

 gardens {Malcobnia) 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 M tiller's Laiitana 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 with being blue. The garden convolvulus 

 opens a blushing white and passes into full purple. 

 In all these and many other cases the general direc- 

 tion 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 whyblue flowers should 

 be specially adapted for fertilisation by their aid. For 

 Mr. A. R. Wallace has shown that colour is most apt 

 to appear or to vary in those parts of plants or animals 

 which have undergone the highest amount of modifi- 

 cation. The markings of the peacock and the argus 

 pheasant come out upon their immensely developed 

 secondary tail-feathers or wing-plumes ; the metallic 

 hues of sun-birds and humming-birds show themselves 

 upon their highly-specialised crests, gorgets, or lap- 

 pets. It is the same with the hackles of fowls, the 

 head-ornaments of fruit pigeons, and the bills of 

 toucans. The most exquisite colours in the insect 

 world are those which are developed on the greatly 

 expanded and delicately-feathered wings of butter- 

 flies ; and the eyt-spots which adorn a few species are 

 usually found on their very highly modified swallow- 

 tail appendages. So, too, with flowers ; those which 



