STEMS AND BRANCHES AND THEIR USES 191 



shorter than the one just below. Such regular growth is 

 characteristic of most of the firs and spruces, and it gives to 

 the crowns of these trees a symmetrical cone shape. The 

 trunk of a pine likewise grows faster than its branches ; but 

 the branches do not grow at so even a rate, especially on an 



FIG. 117. The white elm (Ulmus americana). 

 Photograph by G. Kemmerer. 



older tree, as do those of the firs and spruces. As a result, the 

 crown of a pine tree, though conical in youth, is likely to 

 become irregular in shape as it grows older. If the trunk 

 does not continue to the top of the tree, but is replaced part- 

 way up by several large branches, the tree has a rounded 

 crown such as is common in the oaks and maples. 



