22 



A PKIMER OF FORESTRY. 



These are the medullary rays, which make the silver 

 grain in qnartered Oak and other woods. (See figs. 17, 

 19, 22, and Pis. VII-IX.) They exist in all kinds of 

 trees, but in many, as, for example, in the Chestnut and 

 in most conifers, they are so tine as hardly to be seen 



.•^« 





Fig. 22.— Slab sawed lengthwise from a Black Oak. Milford, Pa. The saw 

 passed almost through the center of the tree, but not quite. The lines of an- 

 nual growtli are cut through obliquely, and the silver grain appears quite 

 plainly, both in the middle and at the sides. 



with the naked eye. Seasoning cracks which run across 

 the rings of growth always follow the lines of these rays, 

 while others most often follow along some annual ring. 



ANNUAL RINGS. 



It is correct to speak of these rings of growth as 

 "annual rings,'" for as long as the tree is growing 

 healthily a ring is formed each year. (See figs. 17, 22, and 



