2 BULLETIN 6S3, TJ. S. DEPARTMEXT OF AGRICULTURE. 
Slippery elm 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 elm, and the softer, more porous 
wood is called "soft elm." Very porous elm wood is often termed 
"water elm" 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 elm, 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 ability to withstand shock. It is difficult 
to split, except slippery elm. 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 eim are 
not available. Table 3 gives, for different elms, the average com- 
