id 



HARDWOOD RECORD 



of the ray connected to the distal portion 

 by a " tongue and groove. ' ' 



If the bark be deciduous, as in the familiar 

 plane or button-ball tree of the London 

 squares, it will naturally be but seldom found 

 upon a log that has travelled, nor will it 

 be otherwise if it be not firmly adherent. 

 Some barks .shrink more rapidly in a vertical 

 direction than the cylinder of wood within, 

 and thus detach themselves, while others are 

 firmly attached to the wood and separated 

 with difSculty. 



The outer surface of the log cor- 

 responds with the inner surface of the bark, 

 unless there is a considerable thickness of 

 bast between them. In any case the mark- 

 ings on this outer surface may not only 

 serve as a means of identification, but also 

 to show in what manner the grain or fibre 

 of the tree runs, whether spirally, as in the 

 lignum vitae, or sinuously, as in the Austral- 

 ian gum trees — both also important items 

 from a technical point of view. 



Beneath the bark of trees many insects 

 find food and shelter, chiefly the larvte of 

 beetles and moths. Some eat their way into 

 the solid wood to form cylindrical holes or 

 galleries such as may occasionally be seen 

 in ebony and the Australian ironbark. Others 

 confine themselves to galleries made in the 

 newly-formed wood immediately beneath the 

 bark, and travel in a peripheral direction 

 only. As the wood removed by these para- 

 sites is still in the living condition, the gaps 

 made in the tissue are promptly filled up 

 ■i\ith a brownish mass of cells almost as soon 

 as they are made. Whether these cells be 

 thyloses or callus, I am not in a position to 

 decide. * ♦ * The resulting brown flecks are 

 as characteristic of the species as any other 

 feature, because the grub is faithful to its 

 special tree and prefers it to all others, 

 therefore as a series of years can scarcely 

 pass without the presence of the grub, no 

 log of wood of a susceptible species of tree 

 will be found without these traces. A sec- 

 tion of English birch will often display 

 these flecks in hundreds. A peculiarity of 

 the flecks is their property of giving" rise 

 to new rays in abundance, sometimes amount- 

 ing to a dense brush-like tail. Similarly the 

 bird's-eye figure of maple arises from the 

 attacks of an insect. In this case the repair 

 of the injury causes a little dimple-like de- 

 pression in the outside of the wood, which is 

 faithfully overlaid by every subsequent an- 

 nual ring. The dimple is therefore a minia- 

 ture hollow, containing a number of strata, 

 and if the wood be sawn tangentially, the 

 top of the hollow Ls removed and the edges 

 of the successive strata exposed in concentric 

 circles, resembling the contours on a geologi- 

 cal map where a bend in the strata has been 

 denuded. The tails or brushes of rays may 

 be seen in either radial or transverse sec- 

 tions, thus indicating their origin, even if 

 the seat of injury be not evident in the 

 specimen examined. 



Having dealt with the general structure 

 of wood, it is necessary to consider the form 

 in which the elements are arranged. It is 

 not the intention here to go into microscopi- 

 cal details concerning the cells themselves. 

 * * * It is enough to say that every 

 part of a piece of wood consists 

 originally of cells, or closed cavities, 

 which in the case of the pores or 

 vessels become modified into tubes; even in 

 these the remains of the original partitions 

 are to be seen. These cells are of various 

 forms; round, polygonal, spindle-shaped, rec- 

 tangular, etc., and are usually characteristic 

 of the tissue they assist in forming, as will 

 be seen when referring to each special class. 

 The chief feature of the wood of all coni- 

 ferous and broad-leaved trees is the system 

 of rays, not only because rays are never 

 absent, but because they are" a most im- 



portant factor in the classification of wood. 



In a piece of beech on a transverse sec- 

 tion, these rays arise m a fine point, increase 

 in width and again decrease until they taper 

 away again to a vanishing point. By ob- 

 ser\-ing the tangential section, as is easily 

 done by removing the bark, it is seen that, 

 though much shorter, they jireserve the same 

 form, i. e., that of a spindle or tip-cat, taper- 

 ing at both ends. Laterally, in a radial 

 section, it is almost impossible to make out 

 their shape, for they never remain unin- 

 jured; still, from their form on the two 

 sections already described, their shape may 

 be deduced. This T believe to be a double- 

 edged, double-ended blade; something re- 

 sembling the outline of a fish, such as the 

 dace or minnow, but of course very much 

 longer in proportion to its depth. * * • 



Tlie form of the rays is an exceedingly 

 important factor in the composition of the 

 ' ' figure of timber, ' ' and a clear idea upon 

 this point will often enable one to deduce 

 the figure from a small fragment of wood 

 taken in any section, such as a chip from the 

 corner of a log. 



The greater number of species of trees 

 liave merely one kind of ray, but in the oaks 

 there are two kinds, large and small. The 

 large rays are usually very broad and deep 

 in a tangential section, and are seen to be 

 composed of an irregular mass of small 

 cells, while the smaller rays, on the contrary, 

 possess much larger cells, usually in a single 

 row one above another, and are difficult to 

 see in any section. Furthermore, the large 

 rays are frequently compound, or composed 

 of many rows of cells, and run direct from 

 point to point, whereas the small rays ap- 

 jiear to avoid all the large pores which lie 

 in their course, or to be pushed aside by 

 them. This latter character is found with 

 great frequency in woods having rays of 

 uniform size, whether they are broad and 

 firm, or merely like fine threads meandering 

 amongst the pores. In point of size the 

 rays may vary considerably from the broad 

 ones in the classes mentioned, through all 

 possible grades to the excessively fine ones 

 of the horse-chestnut. They vary greatly 

 in the same piece of wood, or in different 

 individuals of the same species, or in the 

 wood of allied species; but like all the other 

 characteristics, there is a limit, a maximum 

 and a minimum, fixed for each kind. It 

 often happens that the limit of length is 

 difficult to fix unless a very large piece 

 of wood is available, as it is not unusual 

 for a ray to extend from ring to ring through 

 thirty years' growth or more before com- 

 mencing to taper. The very large rays often 

 seem to dilate outwards indefinitely and in 

 some cases may do so, while others run their 

 course in the space of two or three annual 

 rings only. 



As the circumference of the annual rings 

 enlarges, the original rays become wider and 

 wider apart, and new rays arise from time 

 to time in sufficient numbers to keep the pro- 

 portion of the rays to the mass of the wood 

 fairly uniform. These new rays obviously 

 have nothing to do with the pith, and being 

 indistinguishable from the okler ones cannot 

 be called in any sense ' ' medullary, ' ' and 

 even those of the first year's wood have not 

 intimate connection with the pith, which 

 may perish entirely without any apparent 

 disturbance of the function of the rays. I 

 therefore use the word rays without the 

 usual qualifying adjective. * * * 



The pores are narrow tubes running ver- 

 tically up the stem, and having the function 

 of conveying air and fluids for the service 

 of the plant. It is not known how long 

 these minute tubes may be. I have blown 

 bubbles through an apparently solid stick 

 of Norwegian birch lour feet long, and I 

 pumped air through the whole length of a 



pole 11% feet long, and further I have 

 pumped water in a continuous stream through 

 a piece of American birch ten inches long 

 by one inch diameter, from which it ran as 

 fast as it would have done from an open 

 tube of Vs inch bore. I see no reason why 

 these limits .should not be exceeded wifb 

 proper apparatus, especially if straight, well- 

 grown, uninjured poles of oak are used. 



In all but the very young wood the pores 

 contain either air or the accumulations of 

 by-products of the vital activity of the 

 leaves, chiefly gums and resins, and some- 

 times a curious tissue like a mass of bubbles, 

 which arises as follows: The walls of the 

 cells and pores, when examined under a 

 high power of magnification, are seen to be 

 pitted all over in spots where the tissue 

 is extremely thin. In fact these pits are 

 holes closed by an excessively thin mem- 

 brane, and are usually opposite to similar 

 perforations in the next adjoining cells or 

 pores. If one of the latter becomes empty, 

 this membrane is forced out into the cavity 

 accompanied by some of the living contents, 

 which subsequently divide and multiply after 

 the manner of the cambium already spoken 

 of as lying under the bark. There is, how- 

 ever, this difference, that instead of wood- 

 cells, they give rise to this bubble-like trans- 

 parent mass of tissue called thyloses. This 

 will frequently be met with in pores of large 

 diameter where the wood has not the prop- 

 erty of filling its pores with gum or resia. 

 Another kind of filling occurs in certain 

 tropical woods, especially teak, and appears 

 to be of a mineral nature. It is very hard 

 and rapidly dulls the edge of cutting tools. 

 In a certain species of wood from British 

 Guiana I have seen accumulations of this 

 substance accompanying decomposition, prac- 

 tically replacing the inner rings of the center 

 of the tree and forming masses of stone 

 weighing many ounces. 



In the course of the building up of the 

 wood by the cambium, the pores are pro- 

 duced at intervals among the wood cells and 

 arise not in haphazard fashion but in rhyth- 

 mic succession. At times they are produced 

 in such abundance and so closely crowded 

 that this rhythm cannot be traced, but * * * 

 in a great many cases a definite order 

 can be seen. The pores may be arranged in 

 undulating festoons, as in the common elm, 

 or in radial, tree-like groups, or as most 

 frequently in our European woods, in a ring 

 of pores in the early Spring zone of the 

 annual ring. For the most part, as already 

 stated, the pores are smaller if not less 

 numerous in the Summer and Autumn zones, 

 the latter being frequently very poorly pro- 

 vided with them. If it should happen that 

 a wood has more pores in the Autumn than 

 in the Spring zone, that wood is surely coni- 

 ferous, but these pores will be found to be 

 of quite different nature to those just de- 

 scribed, in fact they are glands containing 

 resin and are more properly called resin- 

 canals or ducts. Their presence is an indi- 

 cation that the species belongs to one of a 

 limited number of genera allied to the pine 

 trees. Many kinds of wood have pores in small 

 closed groups which convey the impression 

 that a mother-pore has become subdivided 

 into a number of pores, not merely pressed 

 or crowded together but clearly indicating 

 a common origin. * * * If the wood be cut in 

 a radial direction, a row of closely arranged 

 pores may be ex-posed at the same time, so 

 that the wood will appear very ' ' coarse- 

 grained. " On the other hand, if the cut 

 be tangential, the radial row of pores will 

 be cut at right angles, and only one of the 

 series will appear on the surface. Confusion 

 can easily arise from this cause, and no 

 small demand is made upon the imagination 

 to reconcile the differences shown by an. 

 oval-pored wood cut on the quarter (radial 



