FLORAL BIOLOGY. 213 



that observations upon flowers and their insect visitors 

 multiply, the less certain seems the evidence of a colour 

 preference among the lower classes of insects. If this be so, 

 it is evident, since the evolution of flowers has gone hand 

 in hand with that of insects, that only in comparatively 

 recent times can the latter have produced any marked 

 effect upon the colours of flowers, and that too mainly in 

 the higher (biological) groups of flowers. Many wind- 

 fertilised flowers, e.g., Rumex, Corylus, the male flowers of 

 many conifers, the females of Abies, etc., exhibit brilliant 

 colouring. So also do the reproductive organs of many 

 cryptogams. 



Again we usually find it stated that the lines and spots 

 of different colours, found upon the corollas of so many 

 flowers, are adaptations to insect visitors — honey-guides, to 

 use Sprengel's term. That they have a value in this way 

 is pretty certain, but variegation is not uncommon in leaves 

 or fruits, and is even found in flowers at points where it 

 can have no reference to the honey. Flowers are very 

 common that possess honey but have no guides, and vice 

 versa. There are many other interesting facts connected 

 with colour in flowers, e.g., the change of colour with age 

 shown by Diervilla ( Weigelia), many Boraginacese, and other 

 flowers. This has been stated to be an adaptation (to show 

 clever insects which flowers are not worth visiting), but is 

 far more probably a simple chemical phenomenon, compar- 

 able to the colour changes seen in leaves and elsewhere. 

 Another curious point is the three different colours (red, 

 white, and blue), shown by the flowers of the common 

 milkwort (Polyga/a). This seems to have some connection 

 with the constitution of the soil, and also with the 

 local nutrition, as all three sometimes occur on one plant. 

 Sufficient, perhaps, has been said to show that we are far 

 indeed from understanding the phenomena of colour in 

 flowers, and that only secondarily and in comparatively few- 

 flowers can they be regarded as adaptations to insects. 

 There is much to indicate that colour phenomena are 

 largely bound up with sex and reproduction ; the chemical 

 changes occurring in the preparation of the reproductive and 



