100 NATURE STUDIES. 



simple and rounded ; it is only by slow steps that a/ 

 leaf thus gets broken up into many divided segments.. 

 In this respect, then, the meadow buttercup cannot 

 be regarded as the simplest member of its class. 

 There are some other buttercups, such as the ivy-leaved 

 crowfoot, which creeps along the mud of ditches, or 

 the lesser celandine, which springs in the meadows in 

 early April, whose leaves are entire and undivided. 

 In the lesser celandine they are almost circular, and in 

 the ivy-leaved crowfoot they are slightly angular ; but 

 both these plants, having plenty of room to spread in 

 the unoccupied fields of spring or the unappropriated 

 ditches, have never felt the necessity for subdivision 

 into minute segments. They have free access to the 

 air and the sunlight, and so they can assimilate to their 

 hearts' content the carbon of which their tissues are 

 built up. It is otherwise, however, when similar 

 plants push out into new situations, less fully supplied 

 with carbonic acid or with sunshine. For example, 

 there is the water-crowfoot, a mere divergent variety 

 of the ivy -leaved species, which has taken to growing 

 in ponds or rivers. Here it cannot obtain the materials 

 for growth so readily as on its native mud-banks ;, 

 and it has been compelled, accordingly, to split up its 

 submerged leaves into long, thin, hair-like filaments ~ 

 but when it reaches the surface, its foliage spreads 

 out once more into the broad ancestral blades of the 

 ivy -leaved crowfoot. It is just the same with the true 

 buttercups. They have taken to growing in the open 

 meadows, where the competition for vegetable food- 



