xv GENERAL ADAPTATIONS 309 



which details are given of the fertilisation of about 400 

 species of alpine plants by insects, while a General 

 Retrospect gives a most valuable summary of the con- 

 clusions and teachings on the whole subject. As regards 

 the general question of the uses and purposes of colour in 

 nature, the late Grant Allen's interesting and philosophical 

 work on The Colour Sense should be studied. Any one who 

 does so will be satisfied of the general truth of Darwin's 

 doctrines though there are a few errors in the details. As an 

 example of the fascinating style of the book I will quote the 

 following paragraph comparing insect-agency with that of 

 man in modifying and beautifying the face of nature. After 

 describing the great alterations man has made, and the large 

 areas he has modified for his own purposes, the author thus 

 proceeds : 



" But all these alterations are mere surface scratches compared 

 with the immense revolution wrought in the features of nature by 

 the unobtrusive insect. Half the flora of the earth has taken the 

 imprint of his likes and his necessities. While man has only tilled 

 a few level plains, a few great river-valleys, a few peninsular mountain 

 slopes, leaving the vast mass of earth untouched by his hand, the 

 insect has spread himself over every land in a thousand shapes, and 

 has made the whole flowering creation subservient to his daily wants. 

 His buttercup, his dandelion, and his meadow-sweet grow thick in 

 every English field. His thyme clothes the hill-side ; his heather 

 purples the bleak grey moorland. High up among the Alpine 

 heights his gentian spreads itself in lakes of blue ; amid the snows 

 of the Himalayas his rhododendrons gleam with crimson light. The 

 insect has thus turned the whole surface of the earth into a bound- 

 less flower-garden, which supplies him from year to year with pollen 

 or honey, and itself in turn gains perpetuation by the baits it offers 

 for his allurement." 



Although I wholly agree with my lamented friend in 

 attributing the origin and development of flowers to the 

 visits of insects, and the consequent advantage of rendering 

 many species of flowers conspicuous and unlike others 

 flowering at the same time, thus avoiding the waste and 

 injury of the frequent crossing of distinct species, yet I do 

 not consider that the whole of the phenomena of colour in 

 nature is thereby explained. 



In my book on Tropical Nature I devoted two chapters 



