Glue, too, plays one of the principal parts in all veneering and works of marqueterie. For this purpose, the workmen usually employ wood with a threaded vein, to which they give the name of "ferulea," from its resemblance to the grain of the giant fennel,[1] this part of the wood being preferred from its being dotted and wavy. In every variety there are some woods to be found that will not take the glue, and which refuse to unite either with wood of the same kind or of any other; the wood of the robur for example. Indeed, it is mostly the case that substances will not unite unless they are of a similar nature; a stone, for instance, cannot be made to adhere to wood. The wood of the service-tree, the yoke-elm, the box, and, in a less degree, the lime, have a particular aversion to uniting with the cornel. All the yielding woods which we have already spoken[2] of as flexible readily adapt themselves to every kind of work; and in addition to them, the mulberry and the wild fig. Those which are moderately moist are easily sawn and cut, but dry woods are apt to give way beyond the part that is touched by the saw; while, on the other hand, the green woods, with the exception of the robur and the box, offer a more obstinate resistance, filling the intervals between the teeth of the saw with sawdust, and rendering its edge uniform and inert; it is for this reason that the teeth are often made to project right and left in turns, a method by which the saw-dust is discharged. The ash is found the most pliable wood of all for working; and, indeed, for making[3] spears it is better even than the hazel, being lighter than the cornel, and more pliable than the wood of the service-tree. The Gallic variety is so supple, that it is employed in the construction of vehicles even. The elm would rival the trunk of the vine[4] for some purposes, were it not that its weight is so much against it.