The Growth of a Tree 



above, as is shown by the dean break made above a twig when 

 it is torn off, and the stubborn tearing of the fibres below down 

 into the older stem. A half hour spent at the woodpile or among 

 the trees with a jack-knife will demonstrate the laws by which 

 the straight grain of wood is diverted by the insertion of limbs. 

 The careful picking up and tearing back of the fibres of bark 

 and wood will answer all our questions. Basswood whose fibres 

 are tough is excellent for illustration. 



When a twig breaks off, the bark heals the wound and the 

 grain becomes straight over the place. Trees crowded in a forest 

 early divest themselves of their lower branches. These die for 

 lack of sun and air, and the trunk covers their stubs with layers 

 of straight-grained wood. Such timbers are the masts of ships, 

 telegraph poles and the best bridge timbers. Yet buried in 

 their heart wood are the roots of every twig, great or small, 

 that started out to grow when the tree was young. These knots 

 are mostly small and sound, so they do not detract from the 

 value of the lumber. It is a pleasure to work upon such a "stick 

 of timber." 



A tree that grows in the open is clothed to the ground with 

 branches, and its grain is found to be warped by hundreds of 

 knots when it reaches the sawmill. Such a tree is an ornament 

 to the landscape, but it makes inferior, unreliable lumber. The 

 carpenter and the wood chopper despise it, for it ruins tools and 

 tempers. 



Beside the natural diversion of straight grain by knots, 

 there are some abnormal forms to notice. Wood sometimes 

 shows wavy grain under its bark. Certain trees twist in grow- 

 ing, so as to throw the grain into spiral lines. Cypresses and gum 

 trees often exhibit in old stumps a veering of the grain to the 

 left for a few years, then suddenly to the right, producing a 

 "cross grain" that defies attempts to split it. 



"Bird's-eye" and "curly maple" are prizes for the furniture 

 maker. Occasionally a tree of swamp or sugar maple keeps 

 alive the crowded twigs of its sapling for years, and forms adven- 

 titious buds as well. These dwarfed shoots persist, never getting 

 ahead further than a few inches outside the bark. Each is the 

 centre of a wood swelling on the tree body. The annual layers 

 preserve all the inequalities. Dots surrounded by wavy rings 

 are scattered over the boards when the tree is sawed. This is 



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