62 THE COLOURS OF FLOWERS. 



ceolarias, the intimate mixture of colours is very notice- 

 able. In the allied tropical Bignonias and Gloxinias 

 we see much the same distribution of hues. Many 

 of the family are cultivated in gardens on account of 

 their bizarre and fantastic shapes and colours. As to 

 the orchids, it is hardly necessary to say anything 

 about their wonderfully spotted and variegated flowers. 

 Even in our small English kinds the dappling is 

 extremely marked, especially upon the expanded and 

 profoundly modified lower lip ; but in the larger 

 tropical varieties the patterns are often quaint and 

 even startling in their extraordinary richness of fancy 

 and apparent capriciousness of design. Mr. Darwin 

 has shown that their adaptations to insects are more 

 intimate and more marvellous than those of any other 

 flowers whatsoever. 



Structurally speaking, the spots and lines on petals 

 seem to be the direct result of high modification ; but 

 functionally, as Sprengel long ago pointed out, they 

 act as honey-guides, and for this purpose they have 

 no doubt undergone special selection by the proper 

 insects. The case is just analogous to that of the 

 peacock's plumes or the wings of butterflies. In 

 either instance, the spots and eye-marks tend to 

 appear on the most highly-modified surfaces ; but 

 they are perpetuated and intensified by special selec- 

 tive action. Among birds and insects, sexual selection 

 performs the work of fixing the colours ; among 

 flowers, the visits of bees and butterflies effect the 

 same end. Lines are comparatively rare on regular 

 flowers, but they tend to appear as soon as the flower 

 becomes even slightly bilateral, and they point directly 

 towards the nectaries. Hence they cannot be mere 



