CHAPTER IX. 



LEAVES. 



Leaves are membraneous or succulent organs, usu- 

 ally of a green colour, arising immediately from the 

 root, or attached to the stem and its branches. The 

 point by which a leaf is attached to the plant is 

 termed its base, the opposite extremity is the summit, 

 the intermediate portion of the leaf is its expansion, 

 and the boundary of the expansion is its margin. The 

 superior surface is more even, and usually of a deeper 

 green ; and the other exhibits more prominently the 

 fibres of the diverging vessels. 



PETIOLE.— The base is frequently prolonged into 

 a footstalk or Petiole, by which the leaf is removed 

 to a greater or less distance from the place of its 

 attachment. The leaf stalk of the Vine is nearly 

 cylindrical, but we more frequently find its superior 

 surface compressed or channelled, and this circum- 

 stance will enable the student to distinguish the foot 

 stalks of compound leaves, from the young branches 

 with which, without regarding this distinction, he 

 would be liable to confound them. The interesting 

 St. Pierre, has with his usual ingenuity, attempted to 

 prove, that the channel of the petiole is designed to 

 convey the water which falls on the leaves, towards 

 the roots of their respective plants. He even says 

 that the form and capacity of this groove, will indicate 

 the quantity of moisture which any individual plant 



