INTRODUCTION. 



xix 



ground be parched and unable to furnish a supply, 

 they absorb as much as will compensate for the 

 deficiency, and return it, duly prepared for the 

 nourishment of every organ which requires food, 

 and so combined with other substances, and in 

 such proportions, that whatever may be needed, 

 be it gum, or resin, or starch, or sugar, or any 

 other of the numberless substances which exist 

 in vegetables, every twig, vessel, and cell is fed 

 as it was when the earth first brought forth the 

 fruit-tree yielding fruit after his kind. 



The vessels nearest the upper surface of the 

 leaf are connected mth the medullary sheath : 

 those beneath with the liber ; and there is good 

 reason to suppose that the cambium is deposited 

 in the position which it occupies, between the 

 bark and the wood, by the returning vessels of 

 the leaf. The cuticle, both on the upper and 

 under surfaces, is plentifully furnished with pores, 

 termed stamata, the precise action of which is 

 much disputed. The petiole is sometimes fur- 

 nished mth a leaf -like appendage termed a stipule, 

 as in the Rose and many spe- 



cies of Willow. The angle 

 between the base of the pe- 

 dicle and the stem is called 



the axil, and is always oc- v . ^"^-^^ 



cupied by a bud, which from >^'[ "v/ 

 its position is said to be ax- % \ 

 illary. A bud in the de- "^i/ 

 ciduous trees of northern I 

 climates is a rudimentary 



shoot enclosed within scales, which serve to pro- 

 tect it from cold and accidents. In young trees 

 it usually produces a spray of leaves similar to 



