LA IV OF PROGRESSIVE COLOURATION. 33 



primitive in organization, such as R. acris (the central 

 form), R. bulbosus, R. repens, R.flammula, R. sceleratus, 

 R. auricomus, R. philonotis, &c. In the lesser celan- 

 dine or pilewort, R. ficaria, there is a slight divergence 

 from the ordinary habit of the genus, in that the 

 petals, instead of being five in number, are eight or 

 nine, while the sepals are only three; and this 

 divergence is accompanied by two slight variations in 

 colour : the outside of the petals tends to become 

 slightly reddish or purplish, and the flowers fade 



FIG. 9. Vertical section of buttercup {Ranunculus acris)', primitive yellow. 



white, much more distinctly than in most other 

 species of the genus. 



There are two kinds of buttercup in England, how- 

 ever, which show us the transition from yellow to white 

 actually taking place under our very eyes. These 

 are the water-crowfoot, R. aquatilis (Fig. 90), and its 

 close ally the ivy-leaved crowfoot, R. hederaceus, whose 

 petals are still faintly yellow toward the centre, but 

 fade away into primrose and white as they approach 

 the edge. We have already noticed that new colours 

 usually appear at the outside, while the claw or base 



D 



