Page:Popular Science Monthly Volume 45.djvu/619

Rh most happily combined; foi% thanks to the plant's economy in making the rosette branches so short, an abundance of material is available for the construction of those elongated ones which are to perform the special work of mechanical support.

In the course of its first year one of these elaborately organized shoots may attain a length of two feet or even more. During this rapid growth only a little wood is formed, but in the young bark there are developed about a dozen strands of tough, elastic fiber, which show as prominent ridges at the surface. These strands continue for a year or so to impart such strength and elasticity to the branch that when bent downward, even to a radius of two or three inches, it will spring back to its original curve. After the second or third year the bark and its fibers become brittle and weak through wear, but in the meantime the wood within, at first so meager, has been increasing, ring upon ring, around the central pith, so that, before the bark has ceased to be of mechanical service, there has already been formed to take its place a tissue possessing fully as much elasticity as the other, and in addition remarkable toughness and durability. These qualities are even more apparent as the wood grows older; so much so, indeed, that it is highly valued in turnery and the manufacture of archers' bows. Thus we see that when a storm comes, the barberry can meet the emergency with branches which yield gracefully so long as they are young, but with age become most effectively resistant.

Still, a moment's consideration of the distribution of strain will show that for all this flexibility and stoutness throughout the length of the branches a serious dismemberment of the plant must ensue if the place of juncture between each long branch and its trunk be not strongly re-enforced. Now, the long branches of the barberry arise each as a continuation of the axis of a rosette branch. While these short branches have only a cluster of leaves to support, they are but weak, brittle affairs, composed chiefly of soft pith with only a sparse supply of woody fibers; but when the short axis comes to serve as the basal part of a long shoot, not only does the wood increase remarkably, but even the pith becomes hard and firm. Moreover, we find throughout the whole plant that, whenever a branch is called upon to sustain a considerable load, its base is proportionately thickened and strengthened, and the same is true to a marked degree of the main trunk at its juncture with the root.

Although with us barberry bushes are for the most part denizens of the open, in Europe they are reported as often growing at the margin of woods. When in this situation, the branches become much more elongated, and, by using the recurved spines as grappling hooks, they climb over the shrubbery encompassing