XI THE SPECIAL COLOURS OF PLANTS 315 



ment which brings them down till they project straight for- 

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

 to hit against the stigmatic surfaces of the next flower visited 

 on Avhich they leave a portion of their jjollen. The whole of 

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

 moth Avill usually have flown to another plant, and thus effect 

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

 tion ■\\dll be lietter understood by referring to the illustration 

 opposite, from Darwin's Fertilisation 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 Avith the very puzzling 

 question — Why AA^ere these innumerable highly complex 

 adaptations produced, Avhen the very same result may be 

 effected — and often is effected — by extremely simple means ? 

 Supposing, as we must do, that all floAvers Avere once of 

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

 did such irregular and often complicated floAvers as the 

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

 the infinitely varied and fantastic orchids ever come into ex- 

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

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

 ness of regular floAvers Avith 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 

 l)ossible solution of this difficult })roblem, Ave have yet to pass 

 in review a large body of curious adaptations connected with 

 insect fertilisation, and Avill first call attention to that portion 

 of the phenomena Avhich throAV some light upon the special 

 colours of ffoAvers in their relation to the various kinds of 

 insects Avhich visit them. For these facts Ave are lai-gely in- 



1 Sue Darwin's Fertilisation of Orchids for the iiumy extraordinary and 

 complex anaiigenients in these plants. 



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

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

 Fertilisatiiyn of Flowers. 



