THE STRUCTURE OF WOOD. 



33 



one side of the tree, usuall)' the south side, is better nourished than 

 the other, Fig. 14, p. 23. 



Tlie normal direction of the fibers of wood is paralk4 to tlie axis 

 of the stem in which they gi-ow. Such wood is called "straight- 

 grained," Fig. 22, but there are many deviations from tliis rule. 

 Whenever the grain of the wood in a board is, in whole or in part, 



Slrai^^lit Grained Loujj-leat 

 Pine (fuU size). 



Fig". 23. Mahog"any, Showing Alter- 

 nalely Twisted Grain (full size). 



oblique to the sides of the board, it is called "cross-grained." An il- 

 lustration of this is a bend in the fibers, due to a bend in the whole 

 tree or to the presence of a neighboring knot. This bend makes the 

 board more difficult to plane. In many cases, probably in more cases 

 than not, the wood fibers twist around the tree. (See some of the 

 logs in Fig. 107, p. 254.) This produces "spiral" or "twisted" grain. 



