LEAVES 



1G9 



Duration of Leaves. In the pine the leaves remain on the 

 tree for two or three years and, since leaves are always 

 present, such trees are called evergreen', in the oak the leaves 

 are persistent since the dead leaves remain on the tree during 

 the winter; in horse-chestnut and English ivy the blade falls 

 but the petiole is persistent for a time. Leaves that fall at 

 the close of the growing season are deciduous. 



FIG. 104. Leaf Variation. Eight leaves of sassafras (Sassafras sassafras), 

 illustrating how leaves of one species may vary. 



Leaf Scars. Leaf scars are extremely variable in form, 

 size, color and number of bundle traces. Leaf scars are in 

 fact so characteristic that it is possible to identify trees and 

 shrubs in winter by means of the leaf scars and buds. 



