21 



SECTION 5. LEAVES. 



1st. Structure and Functions of Leaves. The leaves of 

 all hardy fruit 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 offices 

 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) y 

 which connects it with 

 the tree or branch on 

 which it is borne, and 

 the expanded part (.4, 

 B, D\ called the blade. 

 The base is the end (O) 

 attached to the stalk, 

 and the apex or point 

 (D) the opposite one. 

 The length is the dis- 

 tance from the base to 

 the point (C to D\ and 

 the width, a line cut- 

 ting the length at riaht 

 angles, and extending 

 from margin to margin 

 (A to }. 



The leaf stalk and 

 its branches, forming 

 the nerves or veins of 

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



Fio. 21. 



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

 leaf stalk. Jl, B, D, the blade. C, the base. 

 D, the point. Line _tf, #, the width. 



