BUDS AND STEMS 



115 



Methods of cutting Timber. — 



A glance at the diagram of the 



sections of timber show us that a 



tree may be cut radially through 



the middle of the trunk, or tan- 



gentially to the middle portion. 



Most lumber is cut tangentially. 



Hence the yearly rings take a 



more or less irregular course. 



The grain of wood is caused by 



the fibers not taking straight 



lines in their course in the tree trunk. In many cases the 



of the wood take a spiral course up the trunk, or they may 



Diagrams of sections of timber: 

 section;' b, radial; c, tangential. 

 Pinchot, U.S. Dept. of Agr.) 



a, cross 

 (From 



fibers 

 wave 



Sections of white pine wood. (From Pinchot, U.S. Dept. of Agr.) 



outward to form little projections. Boards cut out of such a 

 piece of wood will show the effect seen in many of the school 



desks, where the annual rings appear to form 

 small elliptical markings. 



Knots. — Knots, as can be seen from the 

 diagram, are branches which at one time 

 started in their outward growth and were for 

 some reason killed. Later, the tree, continu- 

 ing in its outward growth, surrounded them 

 and covered them up. A dead limb should 

 be pruned before such growth occurs. The 



Section of tree trunk , . • i • i » i i i 



showing knot. markmgs m bird s-eye maple are caused by 



