16 TREES OF THE NORTHERN UNITED STATES 



truok form another distinctive feature. Thus the up- 

 ward sloping branches of the Elm form a striking con- 

 trast to the horizontal or downward sloping branches of 

 the Sour Gum, or, better still, to certain varieties of Oaks. 

 When the main trunk of a tree extends upward 

 through the head to the tip, as in Fig. 3, it is said to be 

 excurrent. When it is soon lost in the division, as in 

 Fig. 4, it is said to be deliquescent. 



