Iv ON PLANT LIFE 145 
In air such leaves would be unable even to 
support their own weight, much less . to 
resist the force of the wind. In still air, 
however, for the same reason, finely-divided 
leaves may be an advantage, while in exposed 
positions compact and entire leaves are more 
suitable. Hence herbaceous plants tend to 
have divided, bushes and trees entire, leaves. 
There are many cases when even in the same 
family low and herb-like species have finely- 
cut leaves, while in shrubby or ligneous ones 
they more or less resemble those of the Laurel 
or Beech. 
These considerations affect trees more than 
herbs, because trees stand more alone, while 
herbaceous plants are more affected by sur- 
rounding plants. Upright ‘leaves tend to be 
narrow, as in the case of grasses; horizontal 
leaves, on the contrary, wider. Large leaves 
are more or less. broken up into leaflets, 
as in the Ash, Mountain-Ash, Horse-Chest- 
nut, etc. . 
The forms of leaves depend also much on 
the manner in which they are packed into the 
buds. 
