504 



BIOLOGY FOR BEGINNERS 



Quarter Grain. In all stems there are pith rays extending from 

 pith to bark, but only in oak, maple, sycamore, and a few others 

 are they large enough to affect the grain of the timber. Since 

 these pith rays run toward the bark, a board cut at (C) would 

 show only their cut ends which would be too small to notice, 

 whereas, if the board be cut at (D) the pith rays will be cut more 

 or less side wise and will show as the plates or flakes which are 

 characteristic of " quartered oak," giving it its beauty and value. 



In order to get as many boards as possible showing this flake 



. FIG. 159. Diagram showing cause of grain in timber and various 

 methods of sawing so as to take advantage of the grain. 



grain (side of pith ray) the logs are sometimes cut in quarters and 

 then sawed from the center outwards so as to show the sides of 

 as many pith rays as possible hence the term " quarter sawed " 

 or " quartered oak." The bastard cut oak, which shows only 

 the annual ring grain (as in A) is sold as " plain " oak and while 

 almost as durable is not nearly as handsome. 



Heart and Sap-wood. As a tree grows larger, only the outer 

 annual rings carry sap in their ducts, while the inner region be- 

 comes practically dead, its only function being support. This 



