98 LEAF-ARRANGEMENT. 



having an area of perhaps 18 inches ; and, corre- 

 sponding with this greater leaf-surface, we find 

 that the twig is somewhat stouter, say .09 of an 

 inch. Following this up we shall find that, cceteris 

 paribus, the size of the leaf has a relation to the 

 thickness of the stem. This is clearly shown in 

 the following table : 



Diameter of Stem Approximate Area of Six 

 in Inches. Upper Leaves in Inches. 



Hornbeam 06 14 



Beech 09 18 



Elm . . . . . . .11 34 



Nut 13 55 



Sycamore 13 60 



Lime 14 60 



Chestnut 15 72 



Mountain Ash 16 60 



Elder 18 93 



Ash 18 100 



Walnut 25 220 



Ailanthus ..... .30 240 



Horsechestnut .... .30 300 



In the Elm the numbers are .11 and 34, in the 

 Chestnut .15 and 72, and in the Horsechestnut 

 the stem has a thickness of .3, and the six leaves 

 have an area often of 300 square inches. Of 

 course, however, these numbers are only approxi- 

 mate. Many things have to be taken into con- 



