Strawberries. 85 



mentil has only five. There is an intermediate form, 

 too, which exactly splits the difference between the 

 two plants in every respect; and one can hardly 

 doubt that tormentil is in reality only a very slightly 

 altered form of cinquefoil, grown woodier and more 

 dwarfish from its peculiar upland situation, and with 

 one of its petals suppressed through gradual failure of 

 constitutional vigour. The frequency with which the 

 first flower on each stem recurs to the original five- 

 petalled form, while the material to spare remains 

 abundant, is very significant : the later flowers, as the 

 material for their formation runs short, have generally 

 to be content with only four petals each. 



JMorc divergent t\-pes of potentilla than these are 

 the forms which have their leaves (to use the technical 

 term) pinnately, not digitately, divided— that is to .say, 

 with the separate leaflets arranged along two sides of 

 a central leaf-stalk instead of radiating from a common 

 point ; and though the white potentilla and the straw- 

 berry belong rather to the latter or digitate division, 

 I shall yet enter briefly into the nature of the pinnate 

 section, for the sake of the light whidi it throws by 

 analogy upon the evolution of our own proper subject, 

 Commonest among the potcntillas of this divergent 

 group in northern Europe is the trailing silverwccd or 

 goosevveed of our English roadsides, a pretty, long- 



