FOLIAGE. 137 



beyond it ; the other base-half, that nearest the trunk, 

 is cut away to fit to the outer margin of the leaf 

 which is below it. 



Thus the difference in the shape of the leaf lobes at 

 the base is of the greatest importance, and is not a 

 mere detail which cannot be explained. In the Elm also 

 there is a curious want of symmetry at the base of the 

 leaf, one half of which comes much lower down the 

 stalk than the other ; but, by placing the branch at 

 the correct angle to the light, it is easy to see how the 

 larger lobe occupies a space which would otherwise 

 allow light to pass. 



The Silverweed {Potentilla anserind) and the Meadow- 

 sweet (ySpirea iilinaria) have rather large leaves for the 

 size of the plants. These leaves are " pinnate," i.e. 

 consist of a series of leaflets arranged along a common 

 stalk. They further possess little supplementary lobes 

 placed along the midrib between the stalks of the leaflet. 

 These supplements are of importance ; if the leaf is 

 slowly turned up and down, it will be found that at a 

 certain angle, corresponding to the direction of light, 

 the small additional lobes exactly fill a vacant space 

 between the stalks of two leaflets. 



On the other hand, when the leaf is free to expand 

 in any direction, as, in the case of the Water Lily, it 

 becomes nearly a circle; for obviously there is no special 

 reason for its growing further in one direction than in 

 another. Kerner and Wiesner and Lubbock (Lord 

 Avebury) give many other examples ; and almost any 

 wood, or hedgerow, or garden, will soon supply material 

 to the student. There are, however, very many 

 apparent exceptions and irregularities, and these are 

 apt to be confusing. Both the beech and the elm are 

 cases in point. The beautiful figure in Kerner's 



