2o6 Flowers and tlieir Pedigrees. 



pollen, and the use of the coloured petals is, in fact, 

 to attract the insects and to induce them to fertilise 

 the seeds. Now, yellow seems to have been the 

 original colour of the petals in almost all (if not 

 absolutely in all) families of flowers ; and the greater 

 number of potentillas are still yellow. But different 

 flowers are visited and fertilised by different insects, 

 and as some insects like one colour and some another, 

 many blossoms have acquired white or pink or purple 

 petals in the place of yellow ones, to suit the particular 

 taste of their insect friends. In tracing the upward 

 course of development in the roses, we shall see that 

 they follow the ordinary law of progressive chromatic 

 changes : the simpler types are yellow ; the somewhat 

 higher ones are white ; the next pink ; and the highest 

 in this particular family are red ; for no rose has yet 

 attained to the final stage of all, which is blue. The 

 colours of petals are always liable to vary, as we all 

 see in our gardens, where florists can produce at will 

 almost any shade or tint that they choose ; and when 

 wild flowers happen to vary in this wa\-, they often 

 get visited by some fresh kind of insect which fertilises 

 their seeds better than the old ones did, and so in 

 time they set up a new variety or a new species. 

 Two of our English potentillas have thus acquired 

 white flowers to suit their proper flies, while one 



