Strazvbei^ries. 87 



Hills in Montgomeryshire, is a mountain species with 

 handsome and conspicuous white blossoms ; and this 

 also is in striking analogy with similar facts elsewhere, 

 for mountain species usually rise higher than their 

 neighbours in the scale of colour, owing to the keen 

 competition between the flowers for the visits of those 

 rare fertilisers, the butterflies, which sail further up 

 mountain heights than the bees and other meadow 

 honeysuckers. For example, some Alpine buttercups 

 are snowy- white, while most of their lowland congeners 

 are simply yellow. 



With the side light thus cast upon our subject by 

 the analogy of the pinnate potentillas, let us hark 

 back to the digitate cinquefoil once more, and ask by 

 what steps some such early ancestral form gave origin 

 to the common predecessor of the true strawberry and 

 its barren sister. The cinquefoil, we saw, had five leaf- 

 lets to each leaf, but the strawberry and the white 

 potentilla have three only. This is one of the marked 

 points wherein these two plants differ from the other 

 potentillas, and agree with one another. But though 

 the trefoil leaf is a matter of some importance, as 

 indicating community of origin, it is not difficult to 

 understand how it has been developed from the primi- 

 tive cinquefoil. The exact number of leaflets in a leaf 

 is always rather variable, depending partly on the 



