FALL OF THE LEAF. 



361 



detachment a small portion of the stalk remains on the branch. This is the case in 

 the so-called Syringa, or Mock Orange (Philadelphus), where the scale-like part 

 which is left has to protect the bud situated just above the leaf -stalk. 



In some trees and shrubs defoliation is very rapid, in others only gradual. In 

 the Japanese Maidenhair Tree (Ginkgo biloba), the formation of the separation-layer 

 and the detachment of the leaves is completed in a few days; in hornbeams and 

 oaks the stripping of the foliage continues for weeks, and frequently only a portion 



Fig. 93. -Leaf -fall of the Horse-chestnut (jEsculus Hippocastanum). 



of the dead leaves is thrown off in the autumn, the remainder not until the close of 

 the winter. 



It is also worthy of remark that in some trees the leaf-faU begins at the end of 

 the branches and gradually proceeds towards the base, while in others the contrary 

 is the case. In ashes, beeches, hazels, and hornbeams, the apices of the branches are 

 leafless when the lower parts stiU bear firmly-fixed foliage; in limes, willows, 

 poplars, and pear-trees, on the other hand, the lower portions of the branches are 

 seen to lose their leaves early in the autumn, the denudation gradually extending 

 upwards; on the extreme ends of the branches some leaves, as a rule, obstinately 

 remain for a long time, until they also are at length whirled away by the first 

 snowstorm. 



