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 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 have flown to another plant, and thus effect 
the most beneficial kind of cross-fertilisation. 1 This descrip¬ 
tion will be better 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 works 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 effected—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; 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 difficult problem, we have j*et to pass 
in review a large body of curious adaptations connected with 
insect fertilisation, and will 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 Darwin’s Fertilisation of Orchids for the many extraordinary and 
complex arrangements in these plants. 
2 The English reader may consult Sir John Lubbock’s British Wild 
Flowers in Relation to Insects, and H. Muller’s great and original work, The 
Fertilisation cf Flowers. 
