(E.) Timber grown in a damp, marshy locality is generally of a poorer quality than that grown upon higher ground, as more water is taken up by the roots than can be well assimilated, which prevents the formation of healthy compact wood. Some woods are adapted to such soil, the poplar or whitewood, willow, basswood, buckeye, and cypress being denizens of moist or swampy places.
Trees growing where they are exposed to winds from one direction are apt to assume a spiral growth, which renders the timber almost worthless, as it is weak, and twists badly in drying.
(F.) Trees which have lumps appearing like growths upon them are usually unhealthy. These lumps, or tumors, may be caused by defective nutrition, checks, or shakes, or by the depredations of animals or insects.
(G.) Clefts, or splits, in a tree may be caused by extreme cold, heat, or drouth. They may extend into the tree several inches, and while the blemish will always remain, showing a discoloration or other defect, nature often repairs it so that the strength of the timber is but slightly affected. If these clefts are not healed, rain may find lodgment there, and the sap be so affected that the adjacent wood will be destroyed, and this in time will destroy the tree.
(H.) Eggs of certain insects are also deposited in these clefts, the larvæ of which bore into the wood and destroy it. (I.) If it were not for the birds and other natural enemies of these insects, they would increase so rapidly that the lumber supply would be seriously affected, and, as it is, there are very few trees which are not injured to some extent by wood borers. The United States Bureau of Entomology estimates that the damage to trees by these pests amounts to at least $100,000,000 annually.
(K.) Sometimes (as at d, Fig. 3) branches die or are broken off; this gives the elements access to the heart of the tree and usually causes a permanent injury, as the birds and other denizens of the forest frequently dig out the rotten wood as soon as the weather has had time to do its work, thus giving further opportunity for decay to continue its destructive action. If this does not happen, the wood will grow over the break after several years and leave a loose knot in the heart of the tree, which will be a decided blemish when the log is made into lumber. The sketch shows the endeavor of nature to repair the defect, as the annual rings will eventually close over the break.
The hard knot at e, Fig. 3, is not a serious defect, unless the wood is to be used for finish or where great strength is required.
7. When to cut lumber.—Trees which are intended for the use of wood-workers should not be felled while the sap is in motion. If cut at any other time than midsummer or in winter, the active sap is apt to sour and to cause decay. Owing to the scarcity of lumber, or from avarice, this precaution often is ignored, and trees are felled at any time of year, regardless of their age; in such cases, much of the lumber lacks the essential qualities of its kind.
When a tree shows signs of dying at the top, it should be cut down, as the quality of the lumber it contains will deteriorate rapidly.
Suggestive Exercises