LEAVES. 21 



Section 5. — Leaves. 



I'st. Structure and Functions of Leaves. — The leaves of 

 all hardy fmit trees cultivated in our climate are decidu- 

 ous, that is — they decay and fall in the autumn and are 

 succeeded by others on the return of spring. The otlices 

 they perform during the growing season .are of the high- 

 est importance to the life and health of the tree, and 

 deserve the most attentive consideration. 



A leaf (fig. 21) is 

 composed of two prin- 

 cipal parts, the leaf 

 stalk or petiole {A\ 

 which connects it with 

 the tree or branch on 

 which it is borne, and 

 the expanded part {A^ 

 D\ called the blade. 

 The hase is the end {C) 

 attached to the stalk, 

 and the apex or 'point 

 {p) the opposite one. 

 The length is the dis- 

 tance from the base to 

 the point {C to and 

 the width^ a line cut- 

 ting the length at right 

 angles, and extending 

 from margin to margin 

 {A to B). 



The leaf stalk and 

 its branches, forming 

 the nerves or veins of 

 the blade, are composed of woody vessels in the foim of 



Fia. 21. 



Fig. 21, a leaf of the pear. A. the petiole or 

 leaf stalk. B, £>, the blade. C, the base. 

 D, the point. Line w2, 8, the width. 



