THE WOOD 219 



usually darkest, but in the picture lightest appearing por- 

 tion, in ash, oak, etc., is spring wood. 



Pores. We have already noticed the conspicuous 

 pores in the spring wood of oak. Besides the larger pores, 

 there are many smaller ones in the same wood. Most of 



FIG. 76. Cross Section of Oak (upper), Ring-Porous Wood ; Hard 

 Pine (lower), Non-Porous Wood 



these are in the summer wood of the rings, so that we 

 have in the oak large pores in the spring wood and small 

 pores in the summer wood, all of which serve as water 

 ducts or vessels when first formed. 



In maple and yellow poplar we can also see pores, but 

 they are extremely small and usually require a magnifying 



