68 TREE TRUNK 



in other woods. When wood is sawed the circles are cut across 

 and appear as grain marks on the boards. In order to show 

 the grain marks, wood used for furniture, ceilings, and floors 

 is often oiled or polished instead of being painted. 



Does the wood on your desk show any grain marks ? Are 

 there any grain marks on the floor or on the walls of the school- 

 room ? By these marks you can tell what kind of wood you 

 have. Of what wood is your desk made ? How many kinds 

 of wood can you see in the schoolroom ? 



Split a knotty stick of wood lengthwise through a knot. 

 Notice how the grain marks on the trunk curve and run up 

 the branch. Why is this ? Has the wood from a small branch 

 layers and grain marks like wood from the trunk of a tree? 



What are the knots in a board ? 



Borers. — In the middle of sticks of firewood there are often 

 tunnels about the size of a leadpencil, or smaller. These tun- 

 nels are usually made by white, black-headed grubs or borers. 

 The borers gnaw tunnels through the w^ood and use some of 

 the chips for food. When full grown they change to winged 

 insects, chiefly beetles. These insects lay eggs which hatch 

 out the boring grubs. 



Borers can usually be found in decaying limbs, but many 

 kinds live in growing trees and spoil the wood with their 

 tunnels. Look for their tunnels in the sawed locust posts of a 

 fence. (See page 45.) Borers often do great damage to fruit 

 trees. Their tunnels are usually near the ground and can be 

 found by means of the sawdust pushed out by the borers. 

 Almost the only way to kill them is by running a wire up 

 the tunnels. 



