16 



LABORATORY AND EIELD EXERCISES 



FIG. 6. Growth of the American elm, an illustration of the spreading 

 type of trees 



The letters from left to right show several stages in the development of the 

 elm. The ultimate form is determined by the hody plan, the method of bud 

 growth, and the pruning effects. The corresponding letters on each figure in- 

 dicate the vigorous (and so successful) branches produced each season. For 

 further discussion consult the text 



(3) Sketch a young elm to show the vigorous branches, 

 which correspond to false whorls in the pines, 

 the annual growths in the length of the main 

 axis, and the weaker branches. Indicate also the 

 scars or other markings where branches have 

 already been naturally or artificially pruned. 



