86 Flowci^s and their Pedigrees. 



leaved plant, with a silvery underside, and bright 

 golden flowers springing from rooted joints on its 

 creeping runners. A rarer plant is the shrubby 

 potentilla, which grows in bushy or stony places, 

 especially on mountain sides, and has accommodated 

 itself to its special situation by acquiring a stout 

 woody stem. This species also has a yellow flower. 

 But there are two other pinnate-leaved English 

 potentillas whose blossoms have long since changed 

 colour under the selective influence of their insect 

 fertilisers. One of these is the marshy comarum, a 

 perennial which grows in peaty or boggy places, and 

 has assumed a dingy purplish-yellow hue, to suit the 

 eyes of marshland insects. It is very noticeable that 

 waterside flies do not seem to care for yellow, and 

 most waterside flowers are therefore pinkish, purplish, 

 or white. Thus the water-crowfoot and the mud- 

 haunting ivy-leaved crowfoot have become white, 

 while all our other native buttercups remain yellow. 

 In the group of bennets or Geums^ closely allied to 

 the potentillas, we find a still closer analogy, for the 

 roadside herb-bennet or common avens is yellow like 

 cinquefoil, but the marshy water-avens has exactly the 

 same dusky purplish-yellow tint as the marshy coma- 

 rum. The other pinnate English potentilla, found 

 wild with us only among the clefts of the Breiddin 



