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. 



