LEAVES. 



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 otiices 

 they perform during the growing season are of the high- 

 est imj)ortance 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^ 

 B^ D\ called the hlade. 

 Tlie hase is the end (6) 

 attached to the stalk, 

 and the apex on' point 

 {D) the opposite one. 

 The length is the dis- 

 tance from the base to 

 the point {C to 2>), and 

 the widths a line cut- 

 ting the length at right 

 angles, and extending 

 from margin to margin 

 {A to B). 



The leaf stalk and 

 its branches, forminar 

 the nerves or veins of 

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



Fig. 21. 



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

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

 D, the point. Line A, B, the width. 



