332 DARWINISM chap. 



and organ, with the enormous powers of increase possessed by 

 plants, have enabled them to become again and again readjusted 

 to each change of condition as it occurred, resulting in that 

 endless variety, that marvellous complexity, and that ex- 

 quisite colouring which excite our admiration in the realm of 

 flowers, and constitute them the perennial charm and crowning 

 glory of nature. 



Flowers the Product of Insect Agency. 



In his Origin of Species, Mr. Darwin first stated that 

 flowers had been rendered conspicuous and beautiful in order 

 to attract insects, adding : " Hence we may conclude that, if 

 insects had not been developed on the earth, our plants would 

 not have been decked with beautiful flowers, but would have 

 produced only such poor flowers as we see on our fir, oak, nut, 

 and ash trees, on grasses, docks, and nettles, which are all 

 fertilised through the agency of the wind." The argument in 

 favour of this view is now much stronger than when he wrote ; 

 for not only have we reason to believe that most of these 

 wind-fertilised flowers are degraded forms of flowers which 

 have once been insect fertilised, but we have abundant evidence 

 that whenever insect agency becomes comparatively ineffective, 

 the colours of the flowers become less bright, their size and 

 beauty diminish, till they are reduced to such small, greenish, 

 inconspicuous flowers as those of the rupture-wort (Herniaria 

 glabra), the knotgrass (Polygonum aviculare), or the cleisto- 

 gamic flowers of the violet. There is good reason to believe, 

 therefore, not only that flowers have been developed in order 

 to attract insects to aid in their fertilisation, but that, having 

 been once produced, in however great profusion, if the insect 

 races were all to become extinct, flowers (in the temperate 

 zones at all events) would soon dwindle away, and that 

 ultimately all floral beauty would vanish from the earth. 



We cannot, therefore, deny the vast change which insects 

 have produced upon the earth's surface, and which has been 

 thus forcibly and beautifully delineated by Mr. Grant Allen : 

 " 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 



