XI THE SPECIAL COLOURS OF PLAXTS 315 



ment Avhich brings them down till they project straight for- 

 ward nearly at right angles to their first position, ro as exactly 

 to Tiit against the stigm atic surfaces of the next flower visited 

 on which they leave a portion of their pollen. The whole of 

 these motions take about half a minute, and in that time the 

 moth will usually ha^'e flown to another plant, and thus eff'ect 

 the most beneficial kind of cross-fertilisation. ^ This descrip- 

 tion will be better understood by referring to the illustration 

 opposite, from Darwin's Feriilisatwn of Orchids (Fig. 30). 



The Interpretation of these Facts. 



Having thus briefly indicated the general character of the 

 more complex adaptations for cross-fertilisation, the details of 

 which are to be found in any of the numerous Avorks on the 

 subject, 2 we find ourselves confronted with the very puzzling 

 cpiestion — Why were these innumerable highly complex 

 adaptations produced, when the very same result may be 

 effected — and often is eff'ected — by extremely simple means ? 

 Supposing, as we must do, that all flowers were once of 

 simple and regular forms, like a buttercup or a rose, how 

 did such irregular and often complicated flowers as the 

 papilionaceous or pea family, the labiates or sage family, and 

 the infinitely varied and fantastic orchids ever come into ex- 

 istence 1 No cause has yet been suggested but the need of 

 attracting insects to cross-fertilise them 5 yet the attractive- 

 ness of regular ■ flowers with bright colours and an ample 

 supply of nectar is equally great, and cross-fertilisation can be 

 quite as effectively secured in these by any of the four simple 

 methods already described. Before attempting to suggest a 

 possible solution of this diflficidt problem, we have yet to pass 

 in review a large body of curious adaptations connected with 

 insect fertilisation, and \n\\ first call attention to that portion 

 of the phenomena which throw some light upon the special 

 colours of flowers in their relation to the various kinds of 

 insects which visit them. For these facts we are largely in- 



1 See Dar^vin's Fertilisation of Orchids for the many extraordiuary and 

 complex arrangements in these plants. 



- The English reader may consult Sir John Lubbock's British JFild 

 Floiuers in Relation to Insects, and H. Mliller's great and original work, The 

 Fertilisation of Flowers. 



