8 



in size with the growth of the tree. In some 

 trees, as the elder, the pith is out of all pro- 

 portion to the surrounding wood ; while in 

 mature oak it is hardly discernible, appearing 

 in the form of a dry, powder-like mass. 

 Radiating from the pith to the bark and pre- 



Pith 



Heartwood 



Sapwood 



Cambium 



Bark 



Medullary rays 



Cross-section of a tree stem. 



senting a star-like appearance are the medullary 

 rays, or " silver-grain " of the carpenter, and 

 it is to the breaking up or crossing of these 

 rays that we owe the beautiful graining of 

 oak and other timbers. Around the pith will 

 be seen a series of consecutive lines or perfect 

 layers, which are the annual rings of wood, 

 the number of which will determine the age 

 of the tree. 



