CO- OPERA TION. 165 



of our garden plants corroborate. It appears to be 

 a law that whenever large numbers of living objects, 

 whether of animals or plants, congregate together, 

 some of them are modified for the benefit of the rest. 

 The transformation of leaves into floral organs, 

 spines, tendrils, etc., is an illustration of the degree to 

 which this is carried out in flowering plants. And, as 

 we shall presently see, even when flowers themselves 

 are grouped in large numbers, some of them undergo 

 marked changes from their brethren. The fact 

 distinguishing human civilisation, that the more 

 advanced it becomes the more it is differentiated, is 

 true also of plants and their flowers. 



The main end and aim of all attractive flowers is, 

 as has already been seen, for the purpose of inducing 

 insects to visit them. The colours and shapes of 

 flowers have been evolved for this purpose ; but we 

 do not know all the numerous reasons why they 

 should have assumed so many different sizes. 



Thus much, however, is evident, that flowers are 

 usually gainers by being grouped together. It has 

 been suggested that the reason why certain kinds of 

 plants are " social " is that their combined masses 

 of colour all the more certainly attract the butter- 

 flies which habitually cross them. This must cer- 

 tainly be the case with the Alpine Gentians, Anemones, 

 and Violets, for bees do not fly to such altitudes. 

 Moreover, it is probable that butterflies have not 

 such keen sight as bees ; and if so, we should expect 



