Wood and Forest

(2) Productive. All practical foresters have as their first aim the yield of the forest. This distinguishes forestry from landscape architecture, the object of which may equally be the preservation and improvement of a given tract. The crop to be produced is as truly the prime concern of the forester as the raising of agricultural crops is the prime concern of the farmer. It is for this reason that forestry is said to be the same thing as conservative lumbering, Fig. 122. The prejudice of lumbermen against forestry has arisen from a misunderstanding of its aim. Its aim is not to prevent the cutting down of trees, but to direct their cutting in such ways that in the future there will still be trees to cut. "Thru use to a greater use," is the motto of the Forest Service. The difference between destructive lumbering and conservative lumbering is that the former cuts one crop regardless of the future; while the latter plans to cut crop after crop indefinitely. In other words, in conservative lumbering, the trees to be cut are not selected solely with reference to their immediate market value. Not one crop, but many, is the forester's motto.

So long as the supply seemed exhaustless, forests might be and were treated as mines are, i.e., exploited for the sake of immediate profit; but now that lumbermen begin to realize that the end of the supply is in sight, more conservative methods are being adopted. We cannot afford to kill the goose that lays the golden eggs. In order then to obtain as rich harvests as possible, the modern forester makes use of various methods, some negative, some positive.

Waste is avoided in all possible ways, stumps are cut low and tops high on the trunk, first class trees are not used for skids, bridges, roads, etc., care is taken in "falling" trees and in dragging out logs, that they will not injure other trees. Just as economical disposal of the log has already been carried to a high degree of perfection in the saw-mill, (see Handwork in Wood, Chapter II,) so one object of forestry is to carry this economy back into the woods.

One of the underlying ideas in conservative lumbering is that the "yield," i.e., the amount of wood taken out of a healthy forest in a given time, shall be equal to the amount grown during the same period. If less is taken out than grows, some trees will overmature and decay; if more is taken out than grows, the forest will ultimately be exhausted.

This principle may be carried out in a number of ways; but in any case it is necessary to know how fast the forest is reproducing itself, and this is one of the functions of the forester. The United States Forest Service makes a definite offer of cooperation with farmers and lumbermen and owners of forests to provide them with skilled foresters for direction in this matter.

In the United States, the most practicable way of determining the yield is by area, i.e., a certain fraction of a forest is to be cut over once in a given length of time, a year or longer. The time between two successive cuttings on the same area must be long enough to allow the young trees left standing to ripen.

In a word, conservative lumbering involves (1) the treatment of the forest as a source of crops, (2) systematic gathering, and (3) young growth so left as to replace the outgo.

The important place that forests fill in the national economy may be realized partly by the citation of a few facts as to the forest products. The lumber industry is the fourth in value of products among the great manufacturing industries of the United States, being exceeded only by the iron and steel, the textile, and the meat industries. It turns out a finished product worth $567,000,000.00. And yet lumber constitutes only about one-half of the value of the total output of forest products. Its annual value is three-fourths of a billion dollars, ($666,641,367 in 1907,) while the annual value of wood fuel, is $350,000,000. More than two-thirds of the people burn wood for fuel. The next largest single item in the list is shingles and laths, $32,000,000. (See Forestry Bulletin No. 74, p. 7.)

Outside of food products, no material is so universally used and so indispensable in human economy as wood. (Fernow, Econ., p. 21.)

The importance of forest products may also be learned from a mere list of the varied uses to which they are put. Such a list would include: fuel, wood and charcoal; houses (over half the population of the United States live in wooden houses); the wooden parts of masonry and steel buildings; scaffolding; barns, sheds and outhouses; ships, with all their parts, and the masts and trim of steel ships, boats and canoes; oars and paddles; railway ties (annual expenditure $50,000,000), railway cars, a million in number; trestles and bridges (more than 2,000 miles in length); posts and fencing; cooperage stock (low estimate, $25,000,000 annually); packing crates, including coffins; baskets; electric wire poles (annual cost about $10,000,000); piles and submerged structures, like canal locks and water-wheels; windmills; mining timbers (yearly cost, $7,500,000), indispensable in all mining operations (for every 100 tons of coal mined, 2 tons of mining timber are needed); street paving; veneers ($5,000,000.00 worth made annually); vehicles, including carriages, wagons, automobiles and sleighs; furniture; machines and their parts; patterns for metal molding; tools and tool handles; musical instruments; cigar boxes; matches; toothpicks; pencils; (315 million a year in the U. S., requiring over 7 million cubic feet of wood); engraving blocks; shoe lasts, shoe trees and parts of shoes; hat blocks; agricultural implements; hop and bean poles; playthings and toys, for both children and adults; Christmas trees and decorations; pipes; walking sticks; umbrella handles; crutches and artificial limbs; household utensils; excelsior.

Products other than wood: Turpentine and resin (worth $20,000,000 a year); tar; oils; tan-bark, 1½ million cords (worth $13,000,000 a year); wood alcohol; wood pulp (worth $15,000,000 a year); nuts; cellulose for collars, combs and car wheels; balsam, medicines; lampblack; dyes; paper fiber (xylolin) for textiles; shellac and varnish ($8,500,000 worth imported in 1907); vinegar and acetic acid; confections (including maple sugar and syrup at $2,500,000 a year).

(3) The Esthetic and sentimental uses of the forest, tho not to be estimated in dollars and cents, are nevertheless of incalculable benefit to the community. They would include the use of the forest as pleasure grounds, for hunting, fishing, camping, photography, and general sightseeing. Notable instances of the growing appreciation of these uses of the forest are the reservation of the Yellowstone and Yosemite Parks as pleasure grounds.

PRESERVATION.

The second object of forestry is the preservation of the forest, or continued reproduction.

In addition to obtaining crops of trees, the forester plans to keep the forest in such condition that it will constantly reproduce itself and never become exhausted.

This does not mean that no forests are to be cut down, or that a given area, once a forest, is to be always a forest. Just as the individual farmer needs some land for fields, some for pasture, and some for woodlots, so the nation needs some for cities, some for farms, some for pleasure grounds, and some for forests. But it does mean that fruitful forests shall not be turned into wildernesses as thousands of square miles now are, by the methods of destructive lumbering.

In general, better land is necessary for agriculture than for forestry, and it is therefore only the part of wisdom to use the better land for fields and reserve the poorer land for forests. There are in the United States enormous regions that are fit for nothing but forests, but many of these, as in Wisconsin, Minnesota, and Michigan, have simply been denuded of their trees and no provision has been made for their reproduction. This then is the second aim of forestry,—to treat the forest so that it will continue to reproduce itself.

In order to obtain this result, certain forest conditions have to be preserved. What these conditions are, we have already noticed (see Chap. V, The Forest Organism). They are partly topographical and climatic and partly historical. They include such factors as, soil, moisture, temperature, and light, the forest cover, the forest floor, the density and mixture of growth, all conditions of forest growth. It is only as the forester preserves these conditions, or to put it otherwise, it is only as he obeys the laws of the forest organism that he can preserve the forest. For a long period of our national history, we Americans were compelled to conform our life and institutions to the presence of the primeval forest, but by long observation of what happens naturally in the forest, there have been developed in Europe and in America certain ways of handling it so as to make it our servant and not our master.

These ways are called silvicultural systems. They are all based on the nature of the forest itself, and they succeed only because they are modifications of what takes place naturally in the woods.

As we have seen above (p. 220) trees reproduce themselves either by sprouts or by seeds. This fact gives rise to two general methods of reproduction, called the coppice systems and the seed systems.

Coppice, Fig. 123. In the simpler form of this system, the forest is divided into a certain number of parts, say thirty, and one part is cut down each year. New sprouts at once start up, which will mature a year later than those in the part cut the previous year. Where the trees of each part are thirty years old at cutting, thirty years is called the "rotation period." The coppice is said to be managed on a thirty-year rotation. The system is widely used in eastern United States, for fuel, posts, charcoal, railway ties, and other small stuff, as well as for tan-bark. This system is modified by maintaining an overwood composed of seedling trees or selected sprouts above a stand of sprouts. This is called the Reserve Sprout method and is used with admirable results by the French.

Seed Forests. In contrast with coppice forests, those raised from seeds produce the best class of timber, such as is used for saw logs.

Seeding from the side, Fig. 124. Many forests naturally spread at their borders from the scattering of their seeds. "Old field pine" is so called from its tendency to spread in this way on old fields. This natural "Seeding from the Side" has given rise to the "Group System," in which an area of ripe trees is cut off and the trees alongside are depended upon to reproduce new ones on the cut-over area. The openings are gradually enlarged until all the old timber is cut out, and the young growth has taken its place. In its best form there is a definite "rotation period," say eighty years. This system is simple, safe, and very useful, especially for small openings in woodlots. A modification of this is the "Strip System," in which long narrow openings, say seventy-five yards wide, are cut out and gradually widened. The strips are cut in the proper direction so that the prevailing winds will cross them, both for the sake of avoiding windfalls and to help scatter the seed. Where the soil is very dry, the strips may run east and west to protect the seedlings from the sun.

Selection Forests. The typical virgin forest, Fig. 125, is one in which trees of all ages are closely intermingled, and it may be either "mixed" or "pure." If a farmer had a woodlot of this character and every year went over it with the ax, cutting out such trees as he needed for his purpose, and also trees whose removal would improve the woods, but taking care not to cut out each year more than the amount of the average growth, he would be using the "Selection System." This system is the best way of keeping a forest dense and of preserving one which is difficult to start afresh, as on a mountain slope; it is practicable where the woods are small or under a high state of care, as in Europe, where this system has been in use for seven centuries. But the cost of road maintenance and of logging is high and it is therefore impracticable in most lumber regions in the United States, except for woods of especial value, like black walnut.

Localized Selection. If instead of the whole forest being treated in this way every year, it were divided up into perhaps twenty parts, and from each part there were taken out each year as much lumber as would equal the annual growth of the whole forest, such a system would be called "Localized Selection." The cost of logging would be greatly reduced and if care were taken to leave standing some seed trees and to cut no trees below a determined size, as twelve inches, the forest would maintain itself in good condition. This system has been applied with great success in certain private forests in the Adirondacks.

Regular Seed Forest or High Forest. In the system already mentioned above of seeding from the side, the trees near the cut areas are depended upon to seed these areas. Moreover, no especial pains are taken to preserve the forest floor and the forest cover. But all trees do not bear seeds annually, nor do their seedlings thrive under such conditions. In other words, in some forests especial pains must be taken to secure reproduction, and the forest conditions must be maintained with special reference to the growing crop. For this purpose, the cuttings take place thru a series of years, sometimes lasting even twenty years. These reproduction cuttings have reference, now to a stimulus to the seed trees, now to the preparation of the seed bed, now to the encouragement of the seedlings. Then later, the old crop is gradually cut away. Later still, in twenty or thirty years, the new forest is thinned, and when it reaches maturity, perhaps in one hundred or two hundred years, the process is repeated. This is called the "Regular Seed Forest." It produces very valuable timber, and has been used for a long time in Switzerland, especially for beech and balsam.

The system is complicated and therefore unsafe in ignorant hands, and the logging is expensive.

Two-storied Seed Forest. A modification of the system of Regular Seed Forest is the planting of another and a tolerant species of tree under older intolerant trees to make a cover for the soil, to prevent the growth of grass and weeds, and to improve the quality of the upper growth.²

An illustration of a natural two-storied seed forest is shown in Fig. 126.

Planting. The planting of forest trees is a comparatively unimportant part of modern forestry. It is a mistaken idea, not uncommon, that the usual way of reproducing forests is to plant trees. It is true that in the pineries of North Germany and in the spruce forests of Saxony, it is common to cut clean and then replant, but it is absurd to conclude, as some have done, that forestry consists of planting a tree every time one is cut. Even if planting were the best method, many more than one tree would have to be planted for each one cut, in order to maintain the forest. So far as America is concerned, not for a long time will planting be much used for reproduction.

The greater portion of American woodlands is in the condition of culled forests, that is, forests from which the merchantable trees have been cut, leaving the younger individuals, as well as all trees belonging to unmarketable species. Even on the areas where the lumbermen have made a clean cut of the original timber, new trees will come up of themselves from seeds blown from the surrounding forests or falling from occasional individuals left standing. (Bruncken, p. 133.)

The usefulness of planting in America is mainly for reclaiming treeless regions, as in the west, and where timber is high priced. The area of planted timber in the Middle West aggregates many hundred thousand acres, once waste land, now converted into useful woods.³

Planting has been made possible in the far west by extensive irrigation systems, and farther east by the lessening of prairie fires, which once set the limit to tree growth in the prairie states. In many parts of Illinois, southern Wisconsin and other prairie States, there is much more forest land than there was twenty-five years ago.

What planting can do, may be seen on some worn out pastures in New England, Fig. 127. With the western movement of agriculture, the abandoned farms of New England are to some extent becoming re-forested, both naturally and by planting, as with white pine, which grows even on sandy soil. Between 1820 and 1880, there was a period of enthusiastic white-pine planting in New England, and tho the interest died on account of the cheap transportation of western lumber, those early plantations prove that white pine can be planted at a profit even on sand barrens. Once worn out and useless pastures are now worth $150 an acre and produce yearly a net income of $3 or more an acre.

IMPROVEMENT.

Besides utilization and preservation, the third main object of forestry is the improvement of the forest. It is not an uncommon mistake to suppose that the virgin forest is the best forest for human purposes. It is a comparatively new idea, especially in America, that a forest can be improved; that is, that better trees can be raised than those which grow naturally. Lumbermen commonly say, "You never can raise a second growth of white pine as good as the first growth." As if this "first growth" were not itself the successsor of thousands of other generations! There is even a legend that white pine will not grow in its old habitat. Says Bruncken,

Many people probably imagine that a primeval wood, "by nature's own hand planted," cannot be surpassed in the number and size of its trees, and consequently in the amount of wood to be derived from it. But the very opposite is true. No wild forest can ever equal a cultivated one in productiveness. To hope that it will, is very much as if a farmer were to expect a full harvest from the grain that may spring up spontaneously in his fields without his sowing. A tract of wild forest in the first place does not contain so many trees as might grow thereon, but only so many as may have survived the struggle for life with their own and other species of plants occupying the locality. Many of the trees so surviving never attain their best development, being suppressed, overshadowed, and hindered by stronger neighbors. Finally much of the space that might be occupied by valuable timber may be given up to trees having little or no market value. The rule is universal that the amount and value of material that can be taken from an area of wild forest remains far behind what the same land may bear if properly treated by the forester. It is certain, therefore, that in the future, when most American forests shall be in a high state of cultivation, the annual output of forests will, from a much restricted area, exceed everything known at the present day. (Bruncken, North American Forests and Forestry, pp. 134-135.)

It is probable that the virgin forest produces but a tithe of the useful material which it is capable of producing. (Fernow, p. 98.)

Mr. Burbank has demonstrated that trees can be bred for any particular quality,—for largeness, strength, shape, amount of pitch, tannin, sugar and the like, and for rapidity of growth; in fact that any desirable attribute of a tree may be developed simply by breeding and selecting. He has created walnut trees, by crossing common varieties, that have grown six times as much in thirteen years as their ancestors did in twenty-eight years, preserving at the same time, the strength, hardness and texture of their forebears. The grain of the wood has been made more beautiful at the same time. The trees are fine for fuel and splendidly adapted to furniture manufacture. (Harwood, The New Earth, p. 179.)

Nature provides in the forest merely those varieties that will survive. Man, by interfering in Nature's processes but obeying her laws, raises what he wants. Nature says: those trees that survive are fit and does not care whether the trees be straight or crooked, branched or clear. Man says: those trees shall survive which are fit for human uses. Man raises better grains and fruits and vegetables than Nature, unaided, can, and, in Europe, better trees for lumber. In America there has been such an abundance of trees good enough for our purposes that we have simply gone out and gathered them, just as a savage goes out to gather berries and nuts. Some day our descendants will smile at our treatment of forests much as we smile at root-digging savages, unless, indeed, we so far destroy the forests that they will be more angered than amused. In Europe and Japan, the original supply of trees having been exhausted, forests have been cultivated for centuries with the purpose of raising crops larger in quantity and better in quality.

There are various methods used in forest improvement. Improvement cuttings, as the name implies, are cuttings made to improve the quality of the forest, whether by thinning out poor species of trees, unsound trees, trees crowding more valuable ones, or trees called "wolves"; that is, trees unduly overshadowing others. Improvement cuttings are often necessary as a preliminary step before any silvicultural system can be applied. Indeed, many of the silvicultural systems involve steady improvement of the forest.

The pruning of branches is a method of improvement, carrying on the natural method by which trees in a forest clean themselves of their branches.

Seeds of valuable species are often sowed, when the conditions are proper, in order to introduce a valuable species, just as brooks and ponds are stocked with fine fish. In general it may be said that improvement methods are only in their infancy, especially in America.

Footnote 1: A concise and interesting statement of the relation of the forest to rain and floods is to be found in Pinchot: Primer of Forestry, Bulletin No. 24, Part II, Chap. III.

Footnote 2: For an interesting account of an application of this method, see Ward, p. 35.

Footnote 3: To encourage such forest extension, the Forest Service is doing much by the publication of bulletins recommending methods and trees suited to special regions, as, e.g., on Forest Planting in Illinois, in the Sand Hill Region of Nebraska, on Coal Lands in Western Pennsylvania, in Western Kansas, in Oklahoma and adjacent regions, etc.

THE USE OF THE FOREST.

• References:*
  • I Utilization.
    • Pinchot, Primer, II, pp. 14-18, 38-48.
    • Bruncken, pp. 121-131, For. Bull. No. 61.
      
      
  •    (1) Protective.
    • Pinchot, Primer, II, pp. 66-73.
    • Craft, Agric. Yr. Bk., 1905, pp. 636-641, (Map. p. 639.)
    • Toumey, Agric. Yr. Bk., 1903, p. 279.
    • Bruncken, pp. 166-173.
    • For. and Irrig., passim.
    • Shaler, I, pp. 485-489.
      
      
  •    (2) Productive.
    • Kellogg, For. Bull., No. 74,
    • Fernow, For. Invest., p. 9.
    • Roth, First Book, p. 133.
    • Zon & Clark, Agric. Yr. Bk., 1907, p. 277.
    • Boulger, pp. 60-76.
    • Roth, Agric. Yr. Bk., 1896, p. 391.
    • Fernow, Economics, pp. 23-33.
      
      
  •    (3) Esthetic.
    • Roth, First Book, p. 180.
      
      
  • II Preservation.
    • Pinchot, Primer, II, pp. 18-36.
    • Bruncken, pp. 95, 190.
    • Graves, For. Bull., No. 26, pp. 67-70.
    • Roth, First Book, pp. 41-76, 193-194.
    • Roth, For. Bull., No. 16, pp. 8, 9.
    • Fernow, Economics, 165-196.
      
      
  •    Planting.
    • Roth, First Book, pp. 76-94, 195-198.
    • Hall, Agric. Yr. Bk., 1902, pp. 145-156.
    • For. Circs., Nos. 37, 41, 45, 81.
    • Bruncken, pp. 92, 133.
    • Forestry Bulletins Nos. 18, 45, 52, 65.
      
      
  • III Improvement.
    • Bruncken, pp. 134-135, 152-160.
    • Graves, For. Bull., No. 26, p. 39.
    • Pinchot, Adirondack Spruce, p. 4.
    • Harwood, pp. 143-181.
      
      

* For general bibliography, see p. 4.

Appendix.

HOW TO DISTINGUISH THE DIFFERENT KINDS OF WOOD.*

By B. E. Fernow and Filibert Roth.

The carpenter or other artisan who handles different woods, becomes familiar with those he employs frequently, and learns to distinguish them thru this familiarity, without usually being able to state the points of distinction. If a wood comes before him with which he is not familiar, he has, of course, no means of determining what it is, and it is possible to select pieces even of those with which he is well acquainted, different in appearance from the general run, that will make him doubtful as to their identification. Furthermore, he may distinguish between hard and soft pines, between oak and ash, or between maple and birch, which are characteristically different; but when it comes to distinguishing between the several species of pine or oak or ash or birch, the absence of readily recognizable characters is such that but few practitioners can be relied upon to do it. Hence, in the market we find many species mixed and sold indiscriminately.

To identify the different woods it is necessary to have a knowledge of the definite, invariable differences in their structure, besides that of the often variable differences in their appearance. These structural differences may either be readily visible to the naked eye or with a magnifier, or they may require a microscopical examination. In some cases such an examination can not be dispensed with, if we would make absolutely sure. There are instances, as in the pines, where even our knowledge of the minute anatomical structure is not yet sufficient to make a sure identification.

In the following key an attempt has been made—the first, so far as we know, in English literature—to give a synoptical view of the distinctive features of the commoner woods of the United States, which are found in the markets or are used in the arts. It will be observed that the distinction has been carried in most instances no further than to genera or classes of woods, since the distinction of species can hardly be accomplished without elaborate microscopic study, and also that, as far as possible, reliance has been placed only on such characteristics as can be distinguished with the naked eye or a simple magnifying glass, in order to make the key useful to the largest number. Recourse has also been taken for the same reason to the less reliable and more variable general external appearance, color, taste, smell, weight, etc.

The user of the key must, however, realize that external appearance, such, for example, as color, is not only very variable but also very difficult to describe, individual observers differing especially in seeing and describing shades of color. The same is true of statements of size, when relative, and not accurately measured, while weight and hardness can perhaps be more readily approximated. Whether any feature is distinctly or only indistinctly seen will also depend somewhat on individual eyesight, opinion, or practice. In some cases the resemblance of different species is so close that only one other expedient will make distinction possible, namely, a knowledge of the region from which the wood has come. We know, for instance, that no longleaf pine grows in Arkansas and that no white pine can come from Alabama, and we can separate the white cedar, giant arbor vitæ of the West and the arbor vitæ of the Northeast, only by the difference of the locality from which the specimen comes. With all these limitations properly appreciated, the key will be found helpful toward greater familiarity with the woods which are more commonly met with.

The features which have been utilized in the key and with which—their names as well as their appearance—therefore, the reader must familiarize himself before attempting to use the key, are mostly described as they appear in cross-section. They are:

(1) Sap-wood and heart-wood (see p. 17), the former being the wood from the outer and the latter from the inner part of the tree. In some cases they differ only in shade, and in others in kind of color, the heart-wood exhibiting either a darker shade or a pronounced color. Since one can not always have the two together, or be certain whether he has sap-wood or heart-wood, reliance upon this feature is, to be sure, unsatisfactory, yet sometimes it is the only general characteristic that can be relied upon. If further assurance is desired, microscopic structure must be examined; in such cases reference has been made to the presence or absence of tracheids in pith rays and the structure of their walls, especially projections and spirals.

(2) Annual rings, their formation having been described on page 19. (See also Figs. 128-130.) They are more or less distinctly marked, and by such marking a classification of three great groups of wood is possible.

(3) Spring wood and summer wood, the former being the interior (first formed wood of the year), the latter the exterior (last formed) part of the ring. The proportion of each and the manner in which the one merges into the other are sometimes used, but more frequently the manner in which the pores appear distributed in either.

(4) Pores, which are vessels cut thru, appearing as holes in cross-section, in longitudinal section as channels, scratches, or identifications. (See p. 23 and Figs. 129 and 130.) They appear only in the broad-leaved, so called, hard woods; their relative size (large, medium, small, minute, and indistinct when they cease to be visible individually by the naked eye) and manner of distribution in the ring being of much importance, and especially in the summer wood, where they appear singly, in groups, or short broken lines, in continuous concentric, often wavy lines, or in radial branching lines.

(5) Resin ducts (see p. 26 and Fig. 128) which appear very much like pores in cross-section, namely, as holes or lighter or darker colored dots, but much more scattered. They occur only in coniferous woods, and their presence or absence, size, number, and distribution are an important distinction in these woods.

(6) Pith rays (see p. 21 and Figs. 129 and 130), which in cross-section appear as radial lines, and in radial section as interrupted bands of varying breadth, impart a peculiar luster to that section in some woods. They are most readily visible with the naked eye or with a magnifier in the broad-leaved woods. In coniferous woods they are usually so fine and closely packed that to the casual observer they do not appear. Their breadth and their greater or less distinctness are used as distinguishing marks, being styled fine, broad, distinct, very distinct, conspicuous, and indistinct when no longer visible by the naked (strong) eye.

(7) Concentric lines, appearing in the summer wood of certain species more or less distinct, resembling distantly the lines of pores but much finer and not consisting of pores. (See Fig. 129.)

Of microscopic features, the following only have been referred to:

(8) Tracheids, a description of which is to be found on page 28.

(9) Pits, simple and bordered, especially the number of simple pits in the cells of the pith rays, which lead into each of the adjoining tracheids.

For standards of weight, consult table on pages 55 and 192; for standards of hardness, table on page 195.

Unless otherwise stated the color refers always to the fresh cross-section of a piece of dry wood; sometimes distinct kinds of color, sometimes only shades, and often only general color effects appear.

* From Forestry Bulletin No. 10, U. S. Department of Agriculture.

HOW TO USE THE KEY.

Nobody need expect to be able to use successfully any key for the distinction of woods or of any other class of natural objects without some practice. This is especially true with regard to woods, which are apt to vary much, and when the key is based on such meager general data as the present. The best course to adopt is to supply one's self with a small sample collection of woods, accurately named. Small, polished tablets are of little use for this purpose. The pieces should be large enough, if possible, to include pith and bark, and of sufficient width to permit ready inspection of the cross-section. By examining these with the aid of the key, beginning with the better-known woods, one will soon learn to see the features described and to form an idea of the relative standards which the maker of the key had in mind. To aid in this, the accompanying illustrations will be of advantage. When the reader becomes familiar with the key, the work of identifying any given piece will be comparatively easy. The material to be examined must, of course, be suitably prepared. It should be moistened; all cuts should be made with a very sharp knife or razor and be clean and smooth, for a bruised surface reveals but little structure. The most useful cut may be made along one of the edges. Instructive, thin, small sections may be made with a sharp penknife or razor, and when placed on a piece of thin glass, moistened and covered with another piece of glass, they may be examined by holding them toward the light.

Finding, on examination with the magnifier, that it contains pores, we know it is not coniferous or non-porous. Finding no pores collected in the spring-wood portion of the annual ring, but all scattered (diffused) thru the ring, we turn at once to the class of "Diffuse-porous woods." We now note the size and manner in which the pores are distributed thru the ring. Finding them very small and neither conspicuously grouped, nor larger nor more abundant in the spring-wood, we turn to the third group of this class. We now note the pith rays, and finding them neither broad nor conspicuous, but difficult to distinguish, even with the magnifier, we at once exclude the wood from the first two sections of this group and place it in the third, which is represented by only one kind, cottonwood. Finding the wood very soft, white, and on the longitudinal section with a silky luster, we are further assured that our determination is correct. We may now turn to the list of woods and obtain further information regarding the occurrence, qualities, and uses of the wood.

Sometimes our progress is not so easy; we may waver in what group or section to place the wood before us. In such cases we may try each of the doubtful roads until we reach a point where we find ourselves entirely wrong and then return and take up another line; or we may anticipate some of the later mentioned features and finding them apply to our specimen, gain additional assurance of the direction we ought to travel. Color will often help us to arrive at a speedy decision. In many cases, especially with conifers, which are rather difficult to distinguish, a knowledge of the locality from which the specimen comes is at once decisive. Thus, northern white cedar, and bald cypress, and the cedar of the Pacific will be identified, even without the somewhat indefinite criteria given in the key.

KEY TO THE MORE IMPORTANT WOODS OF NORTH AMERICA.

I. Non-porous woods—Pores not visible or conspicuous on cross-section, even with magnifier. Annual rings distinct by denser (dark colored) bands of summer wood (Fig. 128).

II. Ring-porous woods—Pores numerous, usually visible on cross-section without magnifier. Annual rings distinct by a zone of large pores collected in the spring wood, alternating with the denser summer wood (Fig. 129).

III. Diffuse-porous woods—Pores numerous, usually not plainly visible on cross-section without magnifier. Annual rings distinct by a fine line of denser summer wood cells, often quite indistinct; pores scattered thru annual ring, no zone of collected pores in spring wood (Fig. 130).

Note.—The above described three groups are exogenous, i.e., they grow by adding annually wood on their circumference. A fourth group is formed by the endogenous woods, like yuccas and palms, which do not grow by such additions.

I.—Non-Porous Woods.

(Includes all coniferous woods.)

Footnote 1: To discover the resin ducts a very smooth surface is necessary, since resin ducts are frequently seen only with difficulty, appearing on the cross-section as fine whiter or darker spots normally scattered singly, rarely in groups, usually in the summer wood of the annual ring. They are often much more easily seen on radial, and still more so on tangential sections, appearing there as fine lines or dots of open structure of different color or as indentations or pin scratches in a longitudinal direction.

Footnote 2: Soft and hard pines are arbitrary distinctions and the two not distinguishable at the limit.

ADDITIONAL NOTES FOR DISTINCTIONS IN THE GROUP.

Spruce is hardly distinguishable from fir, except by the existence of the resin ducts, and microscopically by the presence of tracheids in the medullary rays. Spruce may also be confounded with soft pine, except for the heart-wood color of the latter and the larger, more frequent, and more readily visible resin ducts.

In the lumber yard, hemlock is usually recognized by color and the silvery character of its surface. Western hemlocks partake of this last character to a less degree.

Microscopically the white pine can be distinguished by having usually only one large pit, while spruce shows three to five very small pits in the parenchyma cells of the pith ray communicating with the tracheid.

The distinction of the pines is possible only by microscopic examination. The following distinctive features may assist in recognizing, when in the log or lumber pile, those usually found in the market:

The light, straw color, combined with great lightness and softness, distinguishes the white pines (white pine and sugar pine) from the hard pines (all others in the market), which may also be recognized by the gradual change of spring wood into summer wood. This change in hard pines is abrupt, making the summer wood appear as a sharply defined and more or less broad band.

The Norway pine, which may be confounded with the shortleaf pine, can be distinguished by being much lighter and softer. It may also, but more rarely, be confounded with heavier white pine, but for the sharper definition of the annual ring, weight, and hardness.

The longleaf pine is strikingly heavy, hard, and resinous, and usually very regular and narrow ringed, showing little sap-wood, and differing in this respect from the shortleaf pine and loblolly pine, which usually have wider rings and more sap-wood, the latter excelling in that respect.

The following convenient and useful classification of pines into four groups, proposed by Dr. H. Mayr, is based on the appearance of the pith ray as seen in a radial section of the spring wood of any ring:

Section I. Walls of the tracheids of the pith ray with dentate projections.