2 BULLETIN 683^ U. S, DEPARTMENT OF AGRICULTURE. 



Slippery elin is so called from its thick mucilaginous inner bark, 

 which distinguishes it from the other elms. The name ^'red elm" is 

 also applied to it. This species is second in importance. Since the 

 wood is quite similar to white elm and the tree is found in practically 

 the same regions, it is generally marketed with white elm under the 

 same name. 



Cork elm, which takes its name from the corky excrescences or 

 growths on the twigs, is also an important commercial species. It is 

 called "rock elm" in the trade. This name is also applied to hard, 

 dense, rapid-growth wood of other species; in fact, very dense wood 

 of any species of elm is called rock ehn, and the softer, more porous 

 wood is called ''soft elm." Very porous elm wood is often termed 

 "water ehn" or "swamp elm." 



Wing elm takes its name from the corky growths on the twigs 

 similar to those on cork elm, which in this species are thin and wing- 

 like. Wing elm is of small importance commercially. 



Cedar ehn, often called "red elm" and in Arkansas "basket elm," 

 is utilized only in a small way, and much of it is not large enough to 

 manufacture into lumber. 



CHARACTERISTICS OF THE WOOD. 



GENERAL APPEARANCE. 



The heartwood of elm is light brown, often tinged with red; the 

 sapwood is lighter. The wood has a fairly distinct and somewhat 

 attractive figure, which is due to bands of pores occurring at the 

 beginning of each annual layer of growth. This figure is incon- 

 spicuous in rock elm because of the smaller size of the pores. The 

 figure varies considerably with the width of annual rings, wood with 

 annual growth layers moderately wide usually yielding the most 

 attractive material. Radial cuts do not give the quartered effect 

 of oak because of the comparatively narrow pith rays. Tangential 

 surfaces present the most pleasing appearance. 



MECHANICAL PROPERTIES. 



The wood of all species of elm is in general heavy, hard, strong, 

 and has in a high degree the abdity to withstand shock. It is difficult 

 to spht, except slippery ehn. It shrinks moderately in seasoning, is 

 one of the best woods for bending, and takes a good polish. Table 1 

 gives the properties of the three principal elm woods expressed in 

 comparative terms. Table 2 shows the results of tests to determine 

 the mechanical properties of the elms, with data for several hickories 

 included for comparison. The table also gives the values of these 

 woods compared to oak. Similar data for wing and cedar elm are 

 not available. Table 3 gives, for different elms, the average com- 



