a_ and _b_). The wood fibres proper, which form the dark,
firm bodies referred to, are very fine, thread-like cells, one
twenty-fifth to one-tenth inch long, with a wall commonly so thick
that scarcely any empty internal space or lumen remains (see Figs. 8,
_e_, and 7, B). If, instead of oak, a piece of poplar or basswood (see
Fig. 9) had been used in this study, the structure would have been
found to be quite different. The same kinds of cell-elements, vessels,
etc., are, to be sure, present, but their combination and arrangement
are different, and thus from the great variety of possible
combinations results the great variety of structure and, in
consequence, of the qualities which distinguish the wood of
broad-leaved trees. The sharp distinction of sap wood and heartwood is
wanting; the rings are not so clearly defined; the vessels of the
wood are small, very numerous, and rather evenly scattered through the
wood of the annual rings, so that the distinction of the ring almost
vanishes and the medullary or pith rays in poplar can be seen, without
being magnified, only on the radial section.

LIST OF MOST IMPORTANT BROAD-LEAVED TREES (HARDWOODS)

Woods of complex and very variable structure, and therefore differing
widely in quality, behavior, and consequently in applicability to the
arts.

AILANTHUS

=1. Ailanthus= (_Ailanthus glandulosa_). Medium to large-sized tree.
Wood pale yellow, hard, fine-grained, and satiny. This species
originally came from China, where it is known as the Tree of "Heaven,"
was introduced into the United States and planted near Philadelphia
during the 18th century, and is more ornamental than useful. It is
used to some extent in cabinet work. Western Pennsylvania and Long
Island, New York.

ASH

Wood heavy, hard, stiff, quite tough, not durable in contact with the
soil, straight-grained, rough on the split surfaces and coarse in
texture. The wood shrinks moderately, seasons with little injury,
stands well, and takes a good polish. In carpentry, ash is used for
stairways, panels, etc. It is used in shipbuilding, in the
construction of cars, wagons, etc., in the manufacture of all kinds of
farm implements, machinery, and especially of all kinds of furniture;
for cooperage, baskets, oars, tool handles, hoops, etc., etc. The
trees of the several species of ash are rapid growers, of small to
medium height with s