EXERCISE 71 

 COMPETITION BETWEEN BRANCHES, AND SELF-PRUNING 



Materials. Several groups of young trees growing close together. 

 The trees should be from ten to twenty-five feet high and must 

 stand close enough to allow the tops to crowd each other a little. 



Directions for work. Examine the group of trees from the 

 outside. It will doubtless be found that they are clothed with' 

 leafy branches almost to the ground. Enter the group and look 

 for the living, leafy branches. What part of the trunk is bear- 

 ing living branches ? Why are there none on other parts of the 

 trunk ? Were there ever branches lower down ? If so, what 

 has happened to them ? Do the dead branches remain on the 

 tree for many years ? Which fall earlier, the large or the small 

 branches ? By studying trees in different situations find out 

 whether the branches die while smaller on trees that are in 

 crowded situations or on those in open places, and which of 

 these situations favors the production of trees with straight, 

 smooth trunks. Which would finally be most suitable for 

 poles and lumber ? 



Study the relation of branches to knots in the wood. If it 

 is allowable to cut down one of the trees, do so, selecting a 

 tree that has a number of good-sized dead branches or branch 

 stubs and some living branches. Cut sections of the trunk in- 

 cluding such branches as mentioned above. Take the pieces to 

 the laboratory and split or saw them lengthwise through the 

 branches. Study the direction of the wood fibers in relation to 

 the living branch. Try to imagine how the grain would run 

 in a plain-sawed board taken from such a part of the tree, and 

 compare with knotty lumber. Would the boards sawed from a 

 tree trunk in the vicinity of the base of a living branch be 

 straight-grained or cross-grained? Would any knot that was 

 found in such a board be a loose knot or a solid one ? In like 

 manner examine the surface split through a dead branch. Note 

 particularly the annual layers of wood in the vicinity of the 

 dead branch. How many years ago did the branch die ? Are 

 the layers of wood formed since then united with the wood of 



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