42 



GENERAL PRINCIPLES. 



Section 5. — Leaves. 



1st. Structure and l^umtions of Leaves. — The leaves, 

 of all hardy fruit trees cultivated in our clim.ite, are de- 

 ciduous — tliat is, 1 1 ley decay and fall in the autumn, and 

 are succeeded by others on the return of spring. The 

 offices tliey perform during the growing season are of 



the liighest importance 

 to the life and health of 

 the tree, and deserve 

 the most attentive con- 

 sideration. 



A leaf (fiu-. 22) is com- 

 posed of two principal 

 parts, the leaf stalky or 

 ]j, petiole {A), which con- 

 nects it witli the tree or 

 branch, on which it irf 

 borne, and the expanded 

 part (i?,r,Z>,^'), called 

 the b'ade. The base is 

 the end (C), attached to 

 the stalk, and the apex, 

 or point {D), the op- 

 posite one. Tlie length 

 is tlic distance from the 



A. the petiole, or leaf .talk; B. C. A E, the ^^^^ ^.O the point ( O tO 

 blade; 6', the base; Z>, the point; Line ^,5, J9), and the Width, a line 



''"^' ^^'^'"'- cutthig the length at 



right angles, and extending from margin to mai'gin {£! 

 to J3). 



The loaf-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 wliich is a pith, similar to the pith of the tree ; the 

 leaf is thus connected with tjie pith and wood of the 



A LEAF OF THE PEAR. 



