THE LEAF. 67 



CHAPTER IV. THE LEAF. 



1. During the previous practical work we 

 have had occasion to observe the structun >. 

 known as leaves, which are borne, on the stems 

 of plants. It is a matter of common know- 

 ledge that the leaves of different plants vary 

 greatly in size, character and shape. But 

 almost all leaves agree in having a more or 

 less thin, flattened, green portion known as 

 the blade of the leaf, which may be simple in 

 shape as a mango leaf or much divided as a 

 tamarind leaf. In many plants, for example 

 the screw-pine, this leaf-blade joins directly 

 on to the stem, but in others it has a thinner, 

 generally rounded, lower portion, the leaf- 

 >/'///, easily seen in a hibiscus or croton. In 

 addition to these two parts many, but by no 

 UK MILS all, leaves show, at the point where they 

 join the stem, a pair of bodies which are known 

 as x///Wrx. These may be very large as in the 

 bread-fruit tree, or very small as in the hibiscus. 



2. The blade of the leaf lias been spoken 

 of so tar as a thin expansion. This is true in 

 by far the greater number of plants, but many 



