II.] GEOLOGICAL ANTIQUITY OF FLOWERS. 45 



Cristagalli, Veronica spicata, Euphrasia Odontites, and 

 E. officinalis, we find that differences have arisen even 

 within the limits of one and the same species. 



In some species, for instance, we find two varieties, 

 one with larger flowers, which are fertilised by 

 insects, and others with smaller flowers, which are 

 self-fertile. 



In other cases the differences between the two kinds 

 of flowers are so marked, and have become so fixed, 



FIG. ^.Malva sylvestris FIG. ^.Malva. rotundifolia. 



that the two kinds are usually considered to be dis- 

 tinct species ; while in yet other cases the differentia- 

 tion is still more complete. 



Among other obvious evidences that the beauty 

 of flowers is useful to them, in consequence of its 

 attracting insects, we may adduce those cases in 

 which the transference of the pollen is effected in 

 different manners in nearly allied plants, some- 

 times even in different species belonging to the 

 same genus. 



