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Stovewood Studies Knots and Knot - Holes

wood, fibers, tree, limb and branch

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If we ignore for a moment the fact that a tree has branches we may think of its animal increase in height and diameter as the slipping on over its head each summer of a hollow cone made of closely packed straight wood libel's. Each year a larger and taller cone would be required to lit the one under it. A cross section of this tree would show the annual rittr.s of growth. If trees were only made without branches there would be rejoicing in the congregation of the wood-workers. The carpenter eould plane a board with his eyes with never a worry about the edge of his too], and the labor of the wood-chopper could be set to music. As an ornament to the landscape, however, sluh a tree would scarcely be considered a success. We turn with satisfaction front the faultless wooden runes to the real tree that spreads its branches all abroad. With all its complexities. the tree still holds this rule of growth. Wood fibers are Mid on in yearly cones between the bark and the I•00(1. The diagrams tell a true story.

It is the branehing habit in trees that makes the knots and knot-holes.

and is responsible for most of the irregularities of the grain of wood.

Each leaf on the little seedling tree bears a bud in its axil. Every bud is a possible branch. The multiplying of leaves. year by yetr, multiplies the number of buds and branches. Every branch began life as a bud. and its ()right can normally 1w traced back into the pith of the stem that bears it. As long as it lives the branch grows in length and thickness exaetly as the 1 tan& does. It adds its wood cones year by year, and shows "them as anima] rings when cut across.

There is no better place to study how trees grow, and to find out the meaning ,)f knots than at the wood pile. Let us go out am! consult the sticks of stovcwood and see how many questions they will suggestto us, and how many they Nvill answer. We shall need a branch with its small twigs for reference when we come to speak of knots, and a pocket knife is indispensable. The axe lies in the block. We shall need to do 'sonic chopping perhaps before we are done.

With our previous notions that the trunk and branches of trees are cylindrical, it is rather disturbing to find that among the misplit wood round sticks are very rare. They are imendish, generally. but often flat tened. Frequently one end is circular and the other oval in outline. Ammal rings are rarely perfect rings. They circle around a point which is nut exactly in the middle. There are twisted sticks and humpy ones—sticks sound from bark to center—others that are mere hollow shells. There are sticks that are smooth

and straight-grained. There are others that are distorted by knots.

What is a knot, anyway, and what, makes a knot-hole? A knot is the base of a branch buried in an older stem. Nor mally. it is just one year younger than its parent stem, for branches rise from buds, and buds are formed in the arils of leaves. The following year the bud unfolds into a leafy shoot, while the stein is taking on its second layer of wood. With each succeed ing year the branch and stein both add wood layers. increasing their diameters. Gradually the base of the limb is swal lowed by the thickening trunk.

When a tree is converted into lumber. knots appear in the boards. They are of all sizes and conditions. There are sound knots of healthy limbs, and black knots caused by disease that entered through an injured limb, and worked down into the heart of the tree. There are loose knots" that fall out, because the cambium was the part the disease attacked. T h 0 stub may be eaten out entirely so that there is no knot at all, but only the knot-hole left. The closing of the outer wound by the healing bark may or may not cheek the disease that is at work within. Let its see how these knots affect the grain of the trunk. Find a stick that has a split surface from Ivhich the stub of a branch projects toward you. The fibers are straight above and below it. They seem to curve out to right and to left and go around the limb. Above. the fibers conic straight, down, and spread abruptly just above the but below. they flare gradually from a point some distance below the knot. A mid dle strip of fibers widens gradually, then flares suddenly so as quite to encompass the limb. The outer fibers of this strip meet above, and run out on the upper side of the limb parallel with each other, the strip, so narrow below, widens and forms a sleeve which fits the limb per fectly. To the right and left of this strip are the fibers of the main stem that go round the knot and meet above it. There is a rather weak joining of the bias edges of this sleeve with these fibers on the main trunk. This is what makes limbs so liable to split away from the main stem. • Often they split by their own weight. Orchard trees break down by the burden of fruit. Sin 1W on evergreens causes similar hreaks—so does the lashing of winds; but those under fibers which unite the trunk and limb do not part.. Often a large limb tears down to the ground and out upon a trunk root before the hold finally breaks.

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