SUMMER FLOWERS 117 



Our knowledge of pigments is still far from satisfactory, 

 but there is considerable evidence that many of them are 

 useless by-products in the economy of the plant. Thus Pro- 

 fessor Vines says : " With regard to their chemical nature, the 

 colouring matters of plants are considered to be closely con- 

 nected with the aromatic group of substances. As to their 

 physiological significance, they may be regarded simply as 

 waste-products in so far as their direct use in constructive 

 metabolism is concerned ; but indirectly they are, in many 

 cases, of great importance. Chorophyll is essential to 

 the process of the formation of organic substance from 

 carbon dioxide and water. The colours of flowers play an 

 important part in attracting insects to visit the flower, and 

 by this means cross-fertilisation is ensured." 



It seems safer at present to avoid general formulation, for 

 there are many indications, both among plants and animals, 

 that pigments have very diverse meanings in the internal 

 economy of the organism. Some are unimportant by- 

 products, of little or no direct internal use after they are 

 formed ; others are very important by-products, of much 

 direct internal use. Some seem to belong to the series of 

 reserve-products, but most seem to be waste-products the 

 ashes of the vital fires. In some flowers the bright colouring 

 means scanty local nutrition; in others, too rapid life; in 

 some, too little moisture ; in others, too much light ; but 

 in the majority it means beauty for ashes. 



As to the general secondary significance of the colour of 

 flowers, there is little doubt it is attractive to insect -visitors 

 This proposition may be upheld without insisting that all 

 floral colour has this meaning, and without implying that 

 the colour affects the insect's eye as it does ours. Grant 

 Allen, in one of his brilliant essays, commits himself to the 

 impetuous and eliptical statement : " Insects produce 

 flowers ; flowers produce insects. The colour-sense pro- 



