Part 9 (1/2)
=111. Long-Leaf Willow= (_Salix fluviatilis_) (Sand Bar Willow). A small-sized tree. Ranges from the Arctic Circle to Northern Mexico.
=112. Bebb Willow= (_Salix bebbiana_ var. _rostrata_). A small-sized tree. More abundant in British America than in the United States, where it ranges southward to Pennsylvania and westward to Minnesota.
=113. Glaucous Willow= (_Salix discolor_) (p.u.s.s.y Willow). A small-sized tree. Common along the banks of streams, and ranges from Nova Scotia to Manitoba, and south to Delaware; west to Indiana and northwestern Missouri.
=114. Crack Willow= (_Salix fragilis_). A medium to large-sized tree.
Wood is very soft, light, very flexible and fairly strong, is fairly durable in contact with the soil, works well and stands well. Used princ.i.p.ally for basket making, hoops, etc., and to produce charcoal for gunpowder. Very common, and widely distributed in the United States.
=115. Weeping Willow= (_Salix babylonica_). Medium- to large-sized tree.
Wood similiar to _Salix nigra_, but not so valuable. Mostly an ornamental tree. Originally came from China. Widely planted in the United States.
YELLOW WOOD
=116. Yellow Wood= (_Cladrastis lutea_) (Virgilia). A small to medium-sized tree. Wood yellow to pale brown, heavy, hard, close-grained and strong. Not used to much extent in manufacturing.
Not common. Found princ.i.p.ally on the limestone cliffs of Kentucky, Tennessee, and North Carolina.
SECTION IV
GRAIN, COLOR, ODOR, WEIGHT, AND FIGURE IN WOOD
DIFFERENT GRAINS OF WOOD
The terms ”fine-grained,” ”coa.r.s.e-grained,” ”straight-grained,” and ”cross-grained” are frequently applied in the trade. In common usage, wood is coa.r.s.e-grained if its annual rings are wide; fine-grained if they are narrow. In the finer wood industries a fine-grained wood is capable of high polish, while a coa.r.s.e-grained wood is not, so that in this latter case the distinction depends chiefly on hardness, and in the former on an accidental case of slow or rapid growth. Generally if the direction of the wood fibres is parallel to the axis of the stem or limb in which they occur, the wood is straight-grained; but in many cases the course of the fibres is spiral or twisted around the tree (as shown in Fig. 15), and sometimes commonly in the b.u.t.ts of gum and cypress, the fibres of several layers are oblique in one direction, and those of the next series of layers are oblique in the opposite direction. (As shown in Fig. 16 the wood is cross or twisted grain.) Wavy-grain in a tangential plane as seen on the radial section is ill.u.s.trated in Fig. 17, which represents an extreme case observed in beech. This same form also occurs on the radial plane, causing the tangential section to appear wavy or in transverse folds.
When wavy grain is fine (_i.e._, the folds or ridges small but numerous) it gives rise to the ”curly” structure frequently seen in maple. Ordinarily, neither wavy, spiral, nor alternate grain is visible on the cross-section; its existence often escapes the eye even on smooth, longitudinal faces in the sawed material, so that the only guide to their discovery lies in splitting the wood in two, in the two normal plains.
[Ill.u.s.tration: Fig. 15. Spiral Grain. Season checks, after removal of bark, indicate the direction of the fibres or grain of the wood.]
[Ill.u.s.tration: Fig. 16. Alternating Spiral Grain in Cypress.
Side and end view of same piece. When the bark was at _o_, the grain of this piece was straight. From that time, each year it grew more oblique in one direction, reaching a climax at _a_, and then turned back in the opposite direction. These alternations were repeated periodically, the bark sharing in these changes.]
Generally the surface of the wood under the bark, and therefore also that of any layer in the interior, is not uniform and smooth, but is channelled and pitted by numerous depressions, which differ greatly in size and form. Usually, any one depression or elevation is restricted to one or few annual layers (_i.e._, seen only in one or few rings) and is then lost, being compensated (the surface at the particular spot evened up) by growth. In some woods, however, any depression or elevation once attained grows from year to year and reaches a maximum size, which is maintained for many years, sometimes throughout life.
In maple, where this tendency to preserve any particular contour is very great, the depressions and elevations are usually small (commonly less than one-eighth inch) but very numerous.
On tangent boards of such wood, the sections, pits, and prominences appear as circlets, and give rise to the beautiful ”bird's eye” or ”landscape” structure. Similiar structures in the burls of black ash, maple, etc., are frequently due to the presence of dormant buds, which cause the surface of all the layers through which they pa.s.s to be covered by small conical elevations, whose cross-sections on the sawed board appear as irregular circlets or islets, each with a dark speck, the section of the pith or ”trace” of the dormant bud in the center.
[Ill.u.s.tration: Fig. 17. Wavy Grain in Beech (_after Nordlinger_).]
In the wood of many broad-leaved trees the wood fibres are much longer when full grown than when they are first formed in the cambium or growing zone. This causes the tips of each fibre to crowd in between the fibres above and below, and leads to an irregular interlacement of these fibres, which adds to the toughness, but reduces the cleavability of the wood. At the juncture of the limb and stem the fibres on the upper and lower sides of the limb behave differently.
On the lower side they run from the stem into the limb, forming an uninterrupted strand or tissue and a perfect union. On the upper side the fibres bend aside, are not continuous into the limb, and hence the connection is not perfect (see Fig. 18). Owing to this arrangement of the fibres, the cleft made in splitting never runs into the knot if started on the side above the limb, but is apt to enter the knot if started below, a fact well understood in woodcraft. When limbs die, decay, and break off, the remaining stubs are surrounded, and may finally be covered by the growth of the trunk and thus give rise to the annoying ”dead” or ”loose” knots.
[Ill.u.s.tration: Fig. 18. Section of Wood showing Position of the Grain at Base of a Limb. P, pith of both stem and limb; 1-7, seven yearly layers of wood; _a_, _b_, knot or basal part of a limb which lived for four years, then died and broke off near the stem, leaving the part to the left of _a_, _b_, a ”sound” knot, the part to the right a ”dead” knot, which would soon be entirely covered by the growing stem.]
COLOR AND ODOR OF WOOD
Color, like structure, lends beauty to the wood, aids in its identification, and is of great value in the determination of its quality. If we consider only the heartwood, the black color of the persimmon, the dark brown of the walnut, the light brown of the white oaks, the reddish brown of the red oaks, the yellowish white of the tulip and poplars, the brownish red of the redwood and cedars, the yellow of the papaw and sumac, are all reliable marks of distinction and color. Together with l.u.s.ter and weight, they are only too often the only features depended upon in practice. Newly formed wood, like that of the outer few rings, has but little color. The sapwood generally is light, and the wood of trees which form no heartwood changes but little, except when stained by forerunners of disease.