Vegetable Physiology. g.» 



rounds a well, inviting the owner and his family to gather be. 

 neath its shade. ' The fruitful bough by a well' is of the high- 

 est antiquity." 



The vine lasts to a considerable age, and spreads to a large 

 extent, or, when supported, rises to a great height. Although 

 it bears plentifully when only three or four years old, it is as- 

 certained that vineyards improve in quality till the age of fifty 

 years. In France and Italy there are vineyards still existing 

 and in full bearing, which were in the same condition at least 

 three centuries ago. In England there are many vines more 

 than 100 years old. The celebrated vine at Hampton Court 

 covers a surface of 22 feet by 72, and seldom bears less than 

 2000 clusters each season, every cluster weighing at least a 

 pound. 



VEGETABLE PHYSIOLOGY. 



NUMBER SIX. 



THE STRUCTURE OF LEAVES. 



The nutritious fluid, taken up by the roots, and diffused 

 through the stem, requires exposure to the air, in order to make 

 it fit for maintaining the life of the plant. Another requisite 

 condition for the same purpose, is the influence of light upon 

 the sap. To effect these objects, the green surface of the plant 

 must necessarily be extended, so as to expose to both air and 

 light a greater portion of the sap than can be done by the sur- 

 face of the stem. The leaf, then, may be said to consist essen- 

 tially of an extension of the skin or cuticle into an expanded 

 surface, supported by a frame-work of ribs or veins prolonged 

 from the woody tissue of the stem or branch, and, like the 

 stem, is composed of cellular tissue, which forms the paren- 

 chyma, or soft portion between the veins, and of woody fibre, 

 which forms the veins themselves. This woody portion has 

 the same office in the leaves as in the stem, giving firmness to 



