HARDWOOD RECORD 



15 



and from British Guiaua come a number of 

 species •which display no indications what- 

 ever of a regular alternation of seasons. 



In most works on forestry much stress 

 is laid upon the width of the annual rings 

 aud careful measurements have been made to 

 ascertain the average width, in order to sup- 

 ply data for estimating the probable annual 

 production of wood. As this is the measure 

 of profit the importance of these iigures 

 cannot be overrated, Ijut inasmuch as they 

 liave little if any value for the purpose of 

 identification, they are only mentioned by 

 the way. The annual increase of rock 

 elm is naturally .slow, perhaps as little as 

 1-16 of an inch per annum, while its near 

 relative tlie white elm is enabled to put 

 on as much as half an inch in the same 

 time, and .seldom less than Vv. inch. 



Mr. Stone calls attention to the fact that 

 a knowledge concerning the rings of growth 

 is useful in tlie study of woods. Some are 

 regular, some are toothed, some are con- 

 volutoil, and the lioundary which may be 

 for:ned liy a fine line of dense Autumn 

 wnoil, a line of contrast between the lax 

 wiiod of Spring following upon the dense 

 ^M>l)d of Autumn, or a similar contrast 

 formed by a pore ring in the .Spring wood, 

 or the boundary may be vague in some 

 woods and entirely fail in others. It must 

 be borne in mind, however, that the boundar- 

 ies of the rings of woods may be very clear 

 at times, and can vary much in the same 

 piece of wood. In an analysis of tree 

 growth care must always be taken to avoid 

 confusing bands of pigment with annual 

 rings. In the rosewoods the black zones are 

 usually concentric, and only on close examin- 

 ation arc they found to be out of harmony 

 with the structure. Another good illustra- 

 tion can be seen in olive wood, often made 

 u]i into articles of virtu and decoration, in 

 which the black zones are always eccentric 

 to a great degree. There is an Australian 

 growth known as the gimlet wood, which in- 

 variably grows on a twist. The true annual 

 rings in this wood are manifest, but as the 

 stem of the tree is three-lobed or buttressed 

 as it were, it gives a very peculiar appearance 

 in the cro.ss section. The silver grain which 

 t'urnis the beautiful flakes so much esteemed 

 in oak timber, and which is composed of 

 fragments of tissue called medullary rays, 

 has the appearance in the cross section, of a 

 giant spider's web. As these rays proceed 

 from the center outward, it is only on those 

 saw-cuts which follow a radical direction — 

 that is, in quarter-sawed lumber — that they 

 appear at their best. As is well known, all 

 woods do not show, this feature in so marked 

 a degree as the oaks. On the contrary, this 

 highly esteemed figure is obscure in most 

 s]>ccies. There is, however, no wood in which 

 it may not be found. There are some kinds 

 "liich do not show the annual rings; others 

 v.hich lack other features present in the 

 oaks, such as the pores or the soft tissue, 

 but none of the conifers or broad-leafed 

 trees can be found that does not show these 

 rays of silver grain. 



To continue the quotation from Mr. Stone's 

 work : 



The pores just mentioned are the little 

 grooves seen upon the surface of cut planks 

 which give to them the appearance known 

 as coarseness of grain. They are little tubes 

 technically called "vessels," whose openings 

 can be seen at the end of a plank, transverse 

 or horizontal section, closely arranged in the 

 annual ring in various ways. The pores be- 

 come smaller and smaller as tliey apijroach 

 the Autumn or outer boundary, until they 

 seem to disappear from very tenuity and 

 both plankwise and across-grain, require a 

 lens to follow them. In the oak, which is 

 the easiest and best example, these smaller 

 pores are arranged in little tree-like patches, 

 imbedded in a mass of light-colored soft 

 tissue. This is composed of short, thiu-walled 

 cells unlike the mass or ground tissue of the 

 wood, which is chiefly built up of long 

 spindle-shaped fibres with thick, w'oody walls, 

 imparting the qualities of hardness and 

 tenacity to the timber. The soft tissue, on 

 the other hand, lacks these properties, but 

 has a peculiar significance, inasmuch as it is 

 frequently the character which declares to 

 which division or group the wood belongs. 

 The conspicuous ' ' pore-ring ' ' the character 

 of which most strikes the eye in many woods, 

 has but a trifling value in this respect, for 

 there are many species of oak in which the 

 pore-ring fails altogether, and even the an- 

 nual ring is difficult to make out, while the 

 little strings of branching pores, along with 

 their attendant soft tissue, are always pres- 

 ent. 



It is a singular fact that as the tree ages 

 the size of its cells and pores increases ring 

 by ring and year by year, so that upon the 

 surface of a plank ' ' cut on the quarter ' ' 

 i. e., in the plane of the radius, very narrow 

 pores lie near the pith and large ones near 

 the bark, with all intermediate sizes between. 

 Thus a plank may be "fine grained" in one 

 part and ' ' coarse grained ' ' in another, 

 whereas if the plank is cut from the out- 

 side of the tree (tangentially) the grain or 

 size of the pores and cells may be nearly 

 uniform throughout. This increase in the 

 size of the pores and cells ceases at a cer- 

 tain age in each species. The oak and hick- 

 ory exliibit this phenomenon in a striking 

 degree. The tree at the period at which this 

 increase stops may be said to be in its prime, 

 for the wood then produced possesses greater 

 strength, weight, tenacity, etc., than that 

 produced either before or after. From a 

 lumberman 's point of view this question of 

 growth is an important one, and it uuist 

 be borne in mind that it is wood and not 

 cavities that the user of timber wants; the 

 greater the proportion of pores, the less 

 wood and the less weight and strength the 

 timber will possess. 



A slow grown piece of oak is a mere suc- 

 cession of pore-rings, i. e., of little tubes, 

 whereas well and fast grown oak has a large 

 proportion of hard woody ground-tissue out- 

 side the pore-ring, in which the rapidly dimin- 

 ishing pores form a comparatively restricted 

 area. There is no strength in holes, and tlie 

 fewer there are the better. In coniferous 

 wood, which is free from true pores, the 

 slowly-grown wood, unlike the faster grown, 

 is small celled and dense. It is merely a 

 question of solid matter of which the weight 

 supplies a good indication. 



The counting of the rings is not an in- 

 fallible indication of age, even when they are 

 counted at the butt of the tree. There are 

 causes which disturb the even succession, 

 such as the destruction of the leaves by in- 

 sects during the growing period, in which 

 case the ring is prematurely closed, much 

 after the manner of usual Autumn cessation 

 of growth. If, as is sometimes the case, the 

 tree has power to put forth fresh leaves, 

 the growth recommences with a pore-ring or 

 other lax tissue, as in the normal Spring 



zone. Thus two rings arise instead of one 

 for the same year. It has been suggested 

 that in tropical climates two independent 

 seasons of growth may cause two fresh rings 

 every year, but the idea needs experimental 

 verification, though not of itself improbable. 

 For the most part the annual rings of tropi- 

 cal trees are difficult to deal with; they are 

 often entirely absent aud no rhythm of 

 structure indicates the periods of growth, 

 and in several instances, to be mentioned 

 later, the pores and other elements steadily 

 increase in size, indefinitely, from the pitli 

 outward to the bark. 



The heart-wood and sap-wood so familiar 

 in the oak, are by no means universal. 

 Familiar examples of trees without heart- 

 wood are the beech, sycamore and birch. 

 American birch, by the w-ay, has both sap- 

 wood and heart-wood. Sometimes the two 

 kinds of wood are distinct from each other, 

 as in the ebony, where the sap is white and 

 the heart black, while in others the former 

 seems to acquire the characteristic colour 

 gradually, and melts insensibly into the 

 darker heart-wood. 



The pith frequently exercises some in- 

 fluence upon the contour of the rings. The 

 common oaks have a five-lobed pith, and the 

 young layers of wood follow it closely, and 

 it is not till the tree has arrived at a con- 

 siderable age that the influence of the pith 

 is lost. The hornbeam retain.s it for an even 

 longer period, and instead of the rings be- 

 coming gradually more regular the lobed 

 form seems to become more jironounced so 

 that the bark, though externally smooth and 

 cylindrical, is internally thickened where 

 the hollows of the waves occur, and is very 

 thin above their crests. 



The pith of all true boxwoods is lozenge- 

 shaped in section, or like a narrow bar with 

 a circular swelling in the middle. The West 

 Indian boxwood, on the contrary, has a round 

 pith that is nearly always cracked, so that 

 this feature is often sufficient to distinguish 

 the true from the false boxwood. All species 

 of walnut have a most remarkable pith con- 

 sisting of a series of diaphragms dividing 

 the tubular cavity into a number of small 

 chambers, as may easily be seen by cutting 

 a twig from a walnut tree. Workmen are 

 familiar with this rather unwelcome peculiar- 

 ity, as it forms a serious defect in the center 

 plank of every log. Although the original 

 pith of the tree-trunk may not often be ac- 

 cessible, yet small knots here and there ex- 

 hibit this feature. 



The bark has always been considered a 

 most useful aid in identifying woods, and in 

 some eases is the only decisive detail. The 

 terms used to describe the bark, such as 

 corky, wrinkled, leathery, fibrous, etc., ex- 

 plain themselves; but as the small breathing 

 holes which perforate it are not familiar ob- 

 jects, the botanical term lenticels must be 

 employed. These lenticels are perhaps most 

 conspicuous upon the bark of the silver 

 birch, where they form the centres of long 

 horizontal stripes, that become longer as the 

 tree increases in girth. Each species of tree 

 has its peculiar kind of lenticel. The bark 

 at the base or butt of the tree frequently 

 differs from that which clothes the upper 

 portion. In the birch again we have an 

 example, for its bark, though smooth and 

 laminated like paper above, is usually rough, 

 fissured and corky at the foot. If a section 

 of the lower part be taken a mass of hard, 

 rod-like, light-coloured bodies will be seen 

 imbedded. This may serve as a type of that 

 which is to be observed in other species, but 

 in addition it must be noted whether the 

 bark is in two distinct layers and also 

 whether the ends of the rays leave their 

 impression upon the inside of the bark, or 

 again, if they are apparently continued some 

 distance into the bark with the woody part 



