8 



BULLETIN 308, U. S. DEPARTMENT OP AGRICULTURE. 



between the hard and soft layers in each annual ring gives the wood 

 a very pleasing figured effect. 



Even under a high-power microscope the woods of the important 

 southern pines appear strikingly similar though not identical in 

 structure. With a view of bringing out the features helpful in dis- 

 tinguishing the wood of shortleaf pine from the other important 

 southern pines, a brief summary of characteristics is given in Table 5. 



Table 5. — Average physical properties of the important southern pines. 





Width 

 of 

 sap- 

 wood. 



Grain (compara- 

 tive width and 

 number of annual 

 rings per 

 inch).i 



Resin content. 



Weight per cubic 

 foot. 



Moisture content. 



Species. 



Green. 



Air- 

 dry 

 (15 

 per 

 cent 

 mois- 

 ture). 



Oven- 

 dry. 



Green. 



Air-dry. 2 





Heart. 



Sap. 



Heart. 



Sap. 



Longleaf 



pine. 

 Slash pine... 

 Shortleaf 



pine 

 Loblolly 



pine. 



Inches. 



2 to 3 



3 to 6 

 3 to 4 



3 to 6 



Narrowest 



(14 rings). 

 Wide 



Very abundant. 

 do 



Lbs. 

 52.5 



52.5 

 45.5 



54.0 



Lbs. 

 43.5 



45.0 

 38.0 



39.0 



Lbs. 

 39.0 



41.5 

 31.0 



36.0 



P.ct. 

 34.0 



32.5 

 31.0 



36.0 



P.ct. 

 95.5 



84.0 

 88.5 



82.0 



P.ct. 

 15 



15 

 15 



15 



P.ct. 



15 



15 



Intermediate 



(11 rings). 

 Widest (7 rings). 



Moderate 



do 



15 

 15 



i Variable in all species so that rapid-growing longleaf might be taken for any of the others. This order 

 prevails in the average. 



2 Heart and sap will ultimately reach the same moisture content if thoroughly air dried under the same 

 conditions. _ 



DURABILITY AND PRESERVATIVE TREATMENT. 



Shortleaf pine is only moderately durable in contact with the 

 soil. The presence of a large amount of resin, as in " light wood," 

 is commonly thought to increase materially the natural durability of 

 the wood. Sap wood is much less durable than heart wood ; it can not 

 ordinarily be expected to last over two or three years, while good 

 heartwood may last seven or eight years. When not in contact with 

 the soil or under conditions particularly conducive to decay, the wood 

 has given good satisfaction. 



By proper preservative treatment the durability of short-leaf pine 

 can be very materially increased. Wood preservation is discussed in 

 a number of publications, among which are Forest Service Bulletins 

 78, 84, 107, 118, and Circular 209. 



MECHANICAL PROPERTIES. 



The wood of shortleaf pine is strong and stiff and therefore very 

 valuable for structural timber. It often contains the same number 

 of rings per inch and is very similar in wood structure to longleaf 

 pine, which holds first place among the southern pines used for this 



