42 



GENERAL PRINCIPLES. 



SECTION 5. LEAVES. 



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

 of all hardy fruit trees cultivated in our climate, are de- 

 ciduous 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 highest importance 

 to the^life and health of 

 the tree, and deserve 

 the most attentive con- 

 sideration. 



A leaf (fig. 22) is com- 

 ^ posed of two principal 

 parts, the leaf -stalk, or 

 petiole (A), which con- 

 nects it with the tree or 

 branch, on which it is 

 borne, and the expanded 

 part (B,C,D,E), called 

 the blade. The base is 

 the end ( C), attached to 

 the stalk, and the apex, 

 or point (D), the op- 

 posite one. The length 

 Fig. 22.-A LEAP OF THE PEAK. the distanoe^from the 



A, the petiole, or leaf stalk; J5, C. D, E, the base to the P Olnt ( 6 to 

 blade ; C', the base ; Z>, the point ; Line E, B, ./)), and the Width, a line 



cutting the length at 

 right angles, and extending from margin to margin (E 



The leaf-stalk and its branches, forming the nerves or 

 veins of the blade, are composed of woody vessels, similar 

 to the woody parts of the tree or branch that bears it, in- 

 side of which is a pith, similar to the pith of the tree ; the 

 leaf is thus connected with the pith and wood of the 



