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FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



'2. Pith rays not or rarely broader than the pores, fine but conspicuous. 



a. Wood heavy and hard, usually of darker reddish color and commonly spotted on cross section. .Red maple. 



b. Wood of medium weight and hardness, usually light colored Silrer maplr. 



Red maple is not always safely distinguished from soft maple. In box elder tho pores are finer and more 



numerous than in soft maple. 



The various species of elm may be distinguished as follows: 



1. Pores of spring wood form a broad band of several rows; easy splitting, dark brown heart lied elm. 



2. Pores of spring wood usually in a single row, or nearly so. 



a. Pores of spring wood large, conspicuously so " kite elm. 



b. Pores of spring wood .small to minute. 



a'. Lines of pores in summer wood fine, not as wide as the intermediate spaces, giving rise to very 



compact grain Rock elm. 



V . Lines of pores broad, commonly as wide as the intermediate spaces Wint/ed elm. 



c. Pores in spring wood indistinct, and therefore hardly a ring-porous wood Cedar dm. 



SU.W. 



;>sp.w. 



Fi<t. 15. Wood of walnut, p. r., pith rays; 

 c. I., concoiitriclincs; v, vessels or port's; 

 MI. ?r., Hummer wood ; xp. w., spring wood. 



Fm. 16 Wood of cherry. 



STKUCTURK OF THE "WOOD OF THE FIVE SOUTHERN PIKES. 1 



The wood of these pines is so much alike in appearance and even in minute structure that 

 it can be discussed largely without distinction of species. The distinctions, as far as there are 

 any, have been pointed out in the introduction. Here it is proposed to give in more detail the 

 characteristics of the wood structure. 



SAP AND HEART WOOD. 



All five species have a distinct sap and heart wood, the sap being light yellow to whitish, the 

 heart yellowish to reddish or orange brown. The line of demarcation between the two is well 

 defined, without any visible transition stage. The location of this line does not as a rule coincide 

 with the line of any annual ring, so that the wood of the same year's growth may be sap on one 

 side of the tree and heart on the other. The difference in this condition may amount to ten or 

 twenty rings, which on one side of the same section will be heart, on the other side sap. 



There is cousiderable variation in the relative width of the two zones as well as the number 

 of rings involved in either and also in the age at which the transition from sap to heart-wood 

 begins. This age was rarely found to be below twenty years; as a rule the transformation begins 

 in young trees when the particular section of the tree is between twenty and twenty-five years 

 old, but the progress of heart formation does not keep pace with the annual growth, being more 

 and more retarded as the tree grows older, so that while in a section twenty-five years old twenty- 

 two rings may be sapwoud, at thirty-five years the sapwood will comprise only thirty rings; at 

 forty-five years, forty rings; at eighty years, fifty rings; and in sections two hundred years old 

 the outer eighty to one hundred rings will still be sap. A young tree of lougleaf pine (No. 22) 

 was, for instance, found to show the following relations: 



1 .Reprinted from Bulletin 13. 



