Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants . It is an organic material , a natural composite of cellulosefibers that are strong in tension and embedded in a matrix of lignin that resists compression. Sometimes Wood is defined as only the secondary xylem in the stems of trees,  or it is defined to include more Broadly the same type of tissue elsewhere Such As in the roots of trees or shrubs. [ quote needed ]In a living tree it performs a support function, enabling woody plants to grow large or to stand up by themselves. It also conveys water and nutrients between the leaves , other growing tissues, and the roots. Wood can also refer to other plant materials with comparable properties, and to material engineered from wood, or wood chips or fiber.
Wood has been used for many years for fuel , as a construction material , for making tools and weapons , furniture and paper , and as a feedstock for the production of purified cellulose and its derivatives, such as cellophane and cellulose acetate .
In 2005, the growing stock of forests worldwide Was about 434 trillion cubic meters, 47% of business qui WAS.  As an abundant, carbon-neutral renewable resource, woody materials have been of intense interest as a source of renewable energy. In 1991, approximately 3.5 billion cubic meters of wood were harvested. Dominant uses were for furniture and building construction. 
A 2011 discovery in the Canadian province of New Brunswick yielded the earliest known plants to have grown wood, approximately 395 to 400 million years ago .  
Wood can be dated by carbon dating and some species by dendrochronology to determine when a wooden object was created.
People-have used wood for Thousands of years For Many Purposes, Including as a fuel or as a building material for making houses , tools , weapons , furniture , packaging , artworks , and paper . Known Constructions using wood dates back ten thousand years. Buildings like the European Neolithic long house were made primarily of wood.
The use of wood has been enhanced by the addition of steel and bronze into construction. 
The year-to-year variation in tree-ring widths and isotopic abundances gives clues to the prevailing climate at the time of a tree was cut. 
Wood, in the strict sense, is yielded by trees , which increases in diameter by the formation, between the existing wood and the inner bark , of new woody layers which envelop the entire stem, living branches, and roots. This process is known as secondary growth ; It is the result of cell division in the vascular cambium , a lateral meristem, and subsequent expansion of the new cells. These cells are mainly composed of cellulose , hemicellulose and lignin .
Where the differences between the four seasons are distinct eg New Zealand , growth in growth rate ; These can usually be more clearly seen on the end of a log, but are also visible on the other surfaces. If the distinctiveness entre annual seasons is (as is the case in equatorial regions eg Singapore ), thesis growth rings are Referred to as annual rings. Where there is little difference in the growth of gold and gold are likely to be indistinct or absent. If the bark of the tree has been removed, the rings will be deformed as the plant overgrows the scar.
If there are differences in a growth ring, then the growth part of the growth of the tree, and the formation of rapid growth, is usually composed of different elements. It is usually lighter in color than that, and is known as earlywood or springwood. The outer portion is known as latewood or summerwood.  However, there are major differences, depending on the kind of wood (see below).
As a tree grows, lower branches often die, and their bases may become overgrown and enclosed by subsequent layers of trunk wood, forming a type of imperfection known as a knot. The dead branch may not be attached to the trunk wood except at its base, and can drop out after the tree has been sawn into boards. Knots affect the technical properties of the wood, usually reducing the local strength and increasing the tendency for splitting along with wood grain, [ citation needed ] but may be exploited for visual effect. In a longitudinally sawn plank, a knot will appear as a circular “solid” (usually dark) piece of wood around which the grainof the rest of the wood “flows” (parts and rejoins). Within a knot, the direction of the grain is up to 90 degrees different from the grain direction of the regular wood.
In the tree a knot is the base of a side branch or dormant bud. A knot (when the base of a side branch) is conical in shape (hence the roughly circular cross-section) with the inner tip of the stem at which the plant’s vascular cambium was located when the branch formed as a bud.
In grading lumber and structural timber, they are classified according to their form, size, soundness, and firmness with which they are held in place. This firmness is affected by, among other factors, the length of time for which the branch was dead while attaching the stem to grow.
Knots materially affecting cracking and warping, ease in working, and cleavability of timber. They are defects which weaken timber and lower value for structural purposes where strength is important. The Weakening effect is much more serious When timber is Subjected to strength perpendicular to the grain and / or voltage than When under load along the grain and / or compression . The extent to which knots affect the strength of a beamdepends on their position, size, number, and condition. A knot on the upper side is compressed, while one on the lower side is subjected to tension. If there is a season in the knot, it is often the case. Small knots, however, may be located along the longitudinal plane of a beam and increase the strength by longitudinal shearing . Knots in a board or plank are at least injurious when they extend through it at right angles to its broadest surface. Knots which occur near the ends of a beam do not weaken it. Sound knots which occur in the central portion of the beam from the edge of the edge.- Samuel J. Record, The Mechanical Properties of Wood 
Knots do not necessarily influence the stiffness of structural timber, this will depend on the size and location. Stiffness and elastic strength are more dependent on localized defects. The breaking strength is very susceptible to defects. Sound knots do not weaken wood when subject to compression parallel to the grain.
In some decorative applications, wood with knots may be desirable to add visual interest. In applications where wood is painted , such as skirting boards, fascia boards, door frames and furniture, resins present in the timber may continue to ‘bleed’ to the surface of a knot for golden brownish stain. A knot primer paint or solution ( knotting ), fully applied during preparation, can do much to reduce this problem but it is difficult to control completely, especially when using mass-produced kiln-dried timber stocks.
Heartwood and sapwood
Heartwood (or duramen  ) is a naturally occurring chemical transformation that has become more resistant to decay. Heartwood formation is a genetically programmed process that occurs spontaneously. Some non-existent practice in the heart of the body, but only once an ounce. 
Heartwood is often visually distinct from the living sapwood, and can be distinguished in a cross-section where the boundary will tend to follow the growth rings. For example, it is sometimes much darker. However, other processes such as decay or insect invasion can also be discolored, even in woody plants that do not form heartwood, which may lead to confusion.
Sapwood (or alburnum  ) is the younger, outermost wood; in the growing tree it is living wood,  and its main functions are to conduct water from the roots to the leavesand to store up and give back to the season. However, by the time they become competent to conduct water, all of them have their cytoplasm and cells are therefore functionally dead. All wood in a tree is first formed as sapwood. The more vigorous growth leaves the sapwood required. So trees making rapid growth in the sapwood for their size in the dense growing forests. Heart of the heart of the heart of the world, 30 cm (12 in) or more in diameter, before any heartwood, for example, in second-growth hickory , or open- grown pines .
The term heartwood derives only from its position and not of any vital importance to the tree. This is evidenced by the fact that a tree can thrive with its heart completely decayed. Some species begin to form heartwood very early in life, so having a thin layer of live sapwood, while in others the change comes slowly. Thin sapwood is characteristic of such species as chestnut, black locust , mulberry , osage-orange , and sassafras , while in maple , ash , hickory , hackberry , beech , and pine, thick sapwood is the rule.  Others never form heartwood.
No definite relationship exists between the annual rings of growth and the amount of sapwood. Within the same species the cross-sectional area of the sapwood is very much proportional to the size of the crown of the tree. If the rings are narrow, they are required. As the tree becomes larger, the sapwood must necessarily become thinner or increase materially in volume. Sapwood is relatively thicker in the upper portion of the trunk of a tree than the base, because the age and the diameter of the lower sections are less.
When a tree is very young it is covered with limbs almost, if not entirely, to the ground, but it is more likely that it will eventually be broken. Subsequent growth of wood may completely conceal the stubs which will however remain as knots. No matter how smooth and clear a log is on the outside, it is more or less knotty near the middle. Therefore, the sapwood of an old tree, and particularly of a forest-grown tree, will be freer from knots than the inner heartwood. Since in their use of wood, they have been weakened because of their position in the woods, it follows that a given piece of sapwood, because of its position in the tree, may well be stronger than a piece of heartwood from the same tree.
It is remarkable that it is important to remember that it is important to remember that it is important to remember that it is important to remember Every broken limb or root, or deep wound from fire, insects, or falling timber, may afford an entrance for decay, which, once started, may be penetrated to all parts of the trunk. The larvae of many insects enter into the trees and their tunnels remain indefinitely as sources of weakness. Whatever the advantages, however, that sapwood may be in this connection.
If a tree grows all its life in the open and the conditions of soiland site remain unchanged, it will make its most rapid growth in youth, and automatically decline. They are narrower and narrower. Since each succeeding ring is predefined, it follows that it is more likely to become a producer of wood. As a tree is lessened, it also reduces the growth rate. In the case of forest-grown trees so much depends on the competition of the trees in their struggle for light and nourishment that periods of rapid and slow growth may alternate. Some trees, such as southern oaks, maintain the same width of the ring for hundreds of years. On the whole, however, as a tree gets larger in the diameter of the growing rings decreases.
Different pieces of wood cut from a large tree. In some trees, the wood on the bottom of the tree is softer, lighter, weaker, and more-than-ready, but the reverse applies. This may or may not correspond to heartwood and sapwood. In a large log the sapwood, because of the time in the life of the tree when it was grown, may be inferior in hardness , strength , and toughness to be equal heartwood of the same log. In a smaller tree, the reverse may be true.
In species which show a difference between heartwood and sapwood the natural color of heartwood is usually darker than that of the sapwood, and very frequently the contrast is conspicuous (see section of yew log above). This is produced by deposits in the heartwood of chemical substances, so that a dramatic difference in the mechanical properties of heartwood and sapwood may not be significantly affected.
Some experiments on very resinous longleaf pine specimens indicate an increase in strength, due to the resin which increases the strength when dry. Such resin-saturated heartwood is called “fat lighter”. Structures built of fat lighter are almost impervious to rot and termites ; however they are very flammable. Stumps of old longleaf are often dug, split into small pieces and sold as kindling for fires. Stumps thus dug may actually remain a century or more since being cut. Spruce impregnated with crude resin and dried is also greatly increased in strength.
Since the latewood of a growth ring is usually darker in color than the earlywood, this fact can be used visually judging the density, and therefore the hardness and strength of the material. This is particularly the case with coniferous woods. In ring-porous woods, the early days of the late nineteenth century are often more severe than those of latewood. Otherwise the color of wood is no indication of strength.
Abnormal discoloration of wood often denotes a diseased condition, indicating unsoundness. The black check in western hemlock is the result of insect attacks. The reddish-brown streaks so common in hickory and some other woods are mostly the result of injury by birds. The discoloration is merely an indication of an injury, and in all probability does not affect the properties of the wood. Certain rot-producing fungi impart to wood characteristic colors which thus become symptomatic of weakness; HOWEVER an attractive effect Known As Spalting produced by this process is regarded Often a desirable characteristic. Ordinary sap-staining is due to fungal growth, but does not necessarily produce a weakening effect.
Water occurs in living wood in three locations, namely:
- in the cell walls ,
- in the protoplasmic contents of the cells
- in the cell cavities and spaces, especially of the xylem
In heartwood it occurs only in the first and last forms. Wood that is thoroughly air-dried retains 8-16% of the water in the cell walls, and none, or practically none, in the other forms. Even oven-dried wood retains a small percentage of moisture, but can be considered absolutely dry.
The general effect of the water content is softer and more pliable. A similar effect occurs in the softening action of water on rawhide, paper, or cloth. Within certain limits, the greater the water content, the greater its softening effect.
Drying produces in the strength of wood, particularly in small specimens. An extreme example is the case of a completely dry spruce block 5 cm in section, which will sustain a steady load of times as much as a green (undried) block of the same size will.
The greatest strength increase in ultimate crushing strength and strength at elastic limit in endwise compression; These are followed by the modulus of rupture, and stress at elastic limit in cross-bending, while the modulus of elasticity is least affected. 
Wood is a heterogeneous , hygroscopic , cellular and anisotropic material. It consists of micro-fibrils of cellulose (40% -50%) and hemicellulose (15% -25%) impregnated with lignin (15% -30%). 
In coniferous or softwood species the wood cells are mostly of one kind, tracheids , and as a result the material is much more in structure than that of most hardwoods . There are no vessels (“pores”) in coniferous wood such as these are prominently in oak and ash, for example.
The structure of hardwoods is more complex.  The water Conducting capability is mostly taken care of by vessels : In Some cases (oak, chestnut, ash) thesis are quite broad and distinct, in others ( buckeye , poplar , willow ) too small to be seen without a hand lens . In discussing such woods it is customary to divide them into two broad classes, ring-porous and diffuse-porous . 
In ring-porous species, such as ash, black locust, catalpa , chestnut, elm , hickory, mulberry , and oak,  the large vessels or pores (as cross sections of vessels are called) are localized in the part of the growth ring formed in spring, thus forming a region of the body of the body. The rest of the ring, produced in summer, is made up of smaller vessels and a much greater proportion of wood fibers. These fibers are the elements which give strength and toughness to wood, while the vessels are a source of weakness. [ quote needed ]
In fact, the pores are still very large in size, and are capable of being separated by the growth ring instead of being collected in a band or row. Examples of this type of wood are alder ,  basswood,  birch ,  buckeye, maple, willow , and Populus species such as aspen, cottonwood and poplar.  Some species, such as walnut and cherry , are on the border between the two classes, forming an intermediate group. 
Earlywood and latewood
In temperate softwoods, there is often a difference between latewood and earlywood. The latewood will be denser than formed early in the season. When examined under a microscope, the cells of dense latewood are seen to be very thick-walled and with very small cell cavities, while those formed in the field of thin walls and large cell cavities. The strength is in the walls, not the cavities. Hence the greater proportion of latewood, the greater density and strength. The principal thing to be considered is the comparative amounts of earlywood and latewood. The width of ring is not nearly so important in the ring.
If a heavy piece of pine is compared to a small piece of paper it will be seen that the heavier one contains a greater proportion of latewood than the other, and is therefore more clearly demarcated growth rings. In white pines there is not much contrast between the different parts of the ring, and the result is very uniform in texture and is easy to work. In hard pines , on the other hand, the latewood is very dense and is deep-colored, presenting a very decided contrast to the soft, straw-colored earlywood.
It is not only the proportion of latewood, but also its quality, that counts. In specimens that show a very large proportion of latewood it is noticeably more important than latewood in rooms that contain less latewood. One can judge comparative density, and therefore to some extent strength, by visual inspection.
No satisfactory explanation can be given for the correct mechanisms determining the formation of earlywood and latewood. Several factors may be involved. In conifers, at least, the rate of growth does not determine the proportion of the two portions of the ring, for in some cases the wood of slow growth is very hard and heavy, while in others the opposite is true. The quality of the site where the tree grows undoubtedly affects the character of the wood form, although it is not possible to formulate a rule governing it. In general, however, it can be said that it is essential, that it should be used.
In ring-porous woods
In ring-porous woods, each season is well defined, because the large pores formed early in the season abut the tissue tissue of the year before.
In the case of the ring-porous hardwoods, there seems to be a definite relationship between the rate of growth of timber and its properties. This can be briefly summed up in the general statement that the growth of growth, the heavier, harder, stronger, and stiffer the wood. This, it must be remembered, applies only to ring-porous woods such as oak, ash, hickory, and others of the same group, and is, of course, subject to some exceptions and limitations.
In ring-porous woods of good growth, it is usually the latewood in which the thick-walled, strength-giving fibers are most abundant. As the breadth of ring diminishes, this latewood is reduced so that comparatively light comparatively light, porous wood composed of thin-walled vessels and wood parenchyma. In good oak, these large chambers of the earlywood occupy from 6 to 10 percent of the volume of the log, while in inferior material they may make up 25% or more. The latewood of good oak is dark colored and firm, and consists mostly of thick-walled fibers which form one-half or more of the wood. In inferior oak, this latewood is much reduced both in quantity and quality. Such variation is very much the result of growth rate.
Wide-ringed wood is often called “second-growth”, because the growth of the young timber in open houses after the old trees has been removed. an important consideration such “second-growth” hardwood material is preferred. This is particularly the case in the choice of hickory for handles and spokes . Here not only strength, but toughness and resilience are important. 
The results of a series of tests on hickory by the US Forest Service show that:
- “The workmanship or shock-resisting ability is greater than that of 5 to 14 rings per inch (rings 1.8-5 mm thick), is fairly constant from 14 to 38 rings per inch (0.7-1.8 mm thick rings) The strength at maximum load is not so great with the most rapid-growing wood rings 1.3-1.8 mm thick), and it is becoming more and more important that the ring is thicker. Thus, the inspector or buyer of hickory should be discriminating against them (less than 1.3 mm thick).in the box of normal growth on dry situations, in which the slow-growing material may be strong and tough. “
The effect of growth rate is as follows:
- “When the rings are wide, the transition from spring wood to summer wood is gradual, while in the narrow rings the spring wood passes into the woods abruptly. the rapid vessels of the summer woods, the rapidity of growth, and the rapidity of the growth of the forest. have more wood substance than slow-growing trees, and have had greater strength in the wood, and the greater the weight of the wood.This agreement is in favor of better delivery and better delivery.
In diffuse-porous woods
In the diffuse-porous woods, the demarcation between rings is not always so clear and in some cases is almost invisible to the unaided eye. Conversely, when there is a clear demarcation there may be a noticeable difference in structure within the growth ring.
In diffused porous woods, they have been stated, the vessels are even-sized, so that the water conducting capability is scattered throughout the ring instead of collected in the earlywood. The effect of spleen growth is, therefore, not the same in the ring-porous woods, approaching more nearly the conditions in the conifers. In general, it can be said that such woods of medium size grow stronger than when grown rapidly. In many uses of wood, total strength is not the main consideration. If ease of working is prized, it should be chosen with a view to its uniformity of texture and straightness of grain, which will be more contrasted between the growth of one season and the growth of the next.
Structural material que resembles ordinary, “dicot” or conifer timber in its gross handling characteristics is produced by a number of monocot plants, and these are colloquially called wood. Of these, bamboo , botanically a member of the grass family, with considerable economic importance, large size being widely used as a building and construction material in their own right, and these days, in the manufacture of engineered flooring, panels and veneer . Another major plant group that produces materials that are often called wood are the palms . Of much less importance are Pandanus , Dracaena and Cordyline .With all this material, the structure and composition of the raw material is quite different from ordinary wood.
The single MOST revealing property of wood as an indicator of wood quality is specific gravity (Timell 1986),  as Both pulp and lumber yield strength are Determined by it. Specific gravity is the ratio of the mass of a substance to the mass of an equal volume of water; is the ratio of a mass of a substance of a substance to a volume of substance, eg grams per milliliter (g / cm 3 or g / ml). The terms are substantially equivalent as long as the metric system is used. After drying, wood shrink and its density increases. These values are associated with green (water-saturated) wood and are referred to as basic specific gravity (Timell 1986). 
Wood density is determined by multiple growth and physiological factors (“Elliott 1970”). 
Age, diameter, height, radial (trunk) growth, geographical location, and growing conditions, silvicultural treatment, and seed source. Variation is to be expected. Within an individual tree, the variation is often greater than that between different trees (Timell 1986).  Variation of specific gravity dans le bole of a tree can Occur In Either the horizontal or vertical direction.
Hard and soft woods
It is common to classify wood as softwood or hardwood . The wood from conifers (eg pine) is called softwood, and the wood from dicotyledons (usually broad-leaved trees, (eg oak) is called hardwood. Necessarily soft. The well-known balsa (a hardwood) is softer than softwood trade Actually any. Conversely, some softwoods (eg yew ) are harder than Many hardwoods.
There is a strong relationship between the properties of wood and the properties of the particular tree that yielded it. The density of wood varies with species. The density of a wood correlates with its strength (mechanical properties). For example, mahogany is a medium-dense hardwood that is excellent for fine furniture crafting, since it is balsa is light, making it useful for model building. One of the densest woods is black ironwood .
Chemistry of wood
50% carbon, 42% oxygen, 6% hydrogen, 1% nitrogen, and 1% other elements (mainly calcium , potassium , sodium , magnesium , iron , and manganese ) by weight.  Wood contains sulfur , chlorine , silicon , phosphorus , and other elements in small quantities.
Aside from water, wood has three main components. Cellulose , a crystalline polymer derived from glucose, about 41-43%. Next in abundance is hemicellulose , which is around 20% in deciduous trees and near 30% in conifers. It is mainly five-carbon sugars that are linked in an irregular manner, in contrast to the cellulose. Lignin is the third component at around 27% in coniferous wood vs. 23% in deciduous trees. Lignin confers the hydrophobic properties reflecting the fact that it is based on aromatic rings. These three components are interwoven, and direct covalent linkages exist between lignin and hemicellulose. A major focus of the paper industry is the separation of the lignin from the cellulose, from which paper is made.
In chemical terms, the difference between hardwood and softwood is reflected in the composition of the lignin . Hardwood lignin is derived from sinapyl alcohol and coniferyl alcohol . Softwood lignin is mainly derived from coniferyl alcohol. 
Aside from the lignocellulose , wood consists of a variety of low molecular weight organic compounds , called extractives . The wood extractives are fatty acids , resin acids , waxes and terpenes .  For example, rosin is exuded by conifers as protection from insects . The extraction of These organic materials from wood Provides tall oil , turpentine , and rosin. 
Wood has a long history of being used as fuel,  which continues to this day, mostly in rural areas of the world. Hardwood is preferred over softwood because it creates less smoke and burns longer. Adding a woodstove or fireplace to a home atmosphere.
Wood has been an important construction material since humans started building shelters, houses and boats. Nearly all boats were made of wood until the late 19th century, and still used today. Elm in particular was used for this purpose as it resisted decay as long as it was kept wet (it also served for water pipe before the advent of more modern plumbing).
Wood to be used for construction work is commonly known as lumber in North America. Elsewhere, lumber usually refers to felled trees, and the word for sawn planks ready for use is timber. In Medieval Europe oak was the wood of choice for all wood construction, including beams, walls, doors, and floors. Today a wider variety of woods is used: solid wood doors are often made from poplar, small-knotted pine, and Douglas fir.
New domestic housing in many parts of the world is commonly made from timber-framed construction. Engineered wood products are becoming a bigger part of the construction industry. They can be used in both residential and commercial buildings as structural and aesthetic materials.
In buildings made of other materials, wood will be found as a supporting material, especially in roof construction, interior doors and frames, and as exterior cladding.
Wood is also commonly used as a shuttering material for the mold in which concrete is forged during reinforced concrete construction.
A solid wood floor is a floor with planks or a piece of timber, usually a hardwood. Since it is hydroscopic (it acquires and loses moisture from the ambient conditions around it), this potential effectively limits the length and width of the boards.
Solid hardwood flooring is usually cheaper than engineered timbers and damaged areas and can be sanded down and refinished repeatedly by the thickness of wood above the tongue.
Solid hardwood floors were originally used for structural purposes, and are used in the construction of solid wooden floors, and are often used in the construction of wood, mosaics and parquetry .
Engineered wood products, engineered products for application-specific performance requirements, are often used in construction and industrial applications. Glued engineered wood products are produced by bonding together wood strands, veneers, lumber or other forms of wood fiber with a larger, more efficient composite structural unit. 
These products include glued laminated timber (glulam), wood structural panels (including plywood , oriented strand board and composite panels), laminated veneer lumber (LVL) and other structural composite lumber (SCL) products, parallel strand lumber , and I-joists.  Approximately 100 million cubic meters of wood was consumed for this purpose in 1991.  The trends suggest that particle board and fiber board will overtake plywood.
Wood can be broken down mechanically (into fibers or chips) or chemically (into cellulose) and used as a raw material for other building materials, such as engineered wood, as well as chipboard , hardboard , and medium -density fiberboard (MDF). Such wood is an important component of the paper, and is used as a component of some synthetic materials . Wood derivatives can be used for flooring, laminate flooring .
Furniture and utensils
Wood has been used extensively for furniture, such as chairs and beds. It is also used for tool handles and cutlery, such as chopsticks , toothpicks , and other utensils, like the wooden spoon and pencil .
Next generation wood products
Further developments include new lignin glue applications, recyclable food packaging, rubber tire replacement applications, anti-bacterial medical agents, and high strength fabrics or composites.  As scientists and engineers further learn and develop new techniques to extract various components from wood, or alternatively to modify wood, for example by adding components to wood, Moisture content electronic monitoring can also enhance next generation wood protection. 
In the arts
Wood has long been used as an artistic medium . It has been used to make sculptures and carvings for millennia. Examples include the totem poles carved by North American Indigenous people from conifer trunks, often Western Red Cedar ( Thuja plicata ).
Other uses of wood in the arts include:
- Woodcut printmaking and engraving
- Wood can be a surface to paint on, such as in panel painting
- Many musical instruments are made mostly or entirely of wood
Sports and recreational equipment
Many types of sports equipment are made of wood, or were made of wood in the past. For example, cricket bats are typically made of white willow . The baseball bats which are legal for use in Major League Baseball are frequently made of ash wood or hickory , and in recent years have been crafted from the fact that wood is somewhat more fragile. NBA shorts have been traditionally made out of parquetry .
Many other types of sports and recreation equipment, such as skis , ice hockey sticks , lacrosse sticks and archery bows , have been made of aluminum, titanium or composite materialssuch as fiberglass and carbon fiber . One noteworthy example of this trend is the family of golf clubs commonly known as the woods , the heads of which were traditionally made of persimmonwood in the early days of the game of golf, but are made of metal or (especially in the case of drivers ) carbon-fiber composites.
Little is known about the bacteria that degrade cellulose. Symbiotic bacteria in Xylophaga may play a role in the degradation of sunken wood; While bacteria such as Alphaproteobacteria , Flavobacteria , Actinobacteria , Clostridia, and Bacteroidetes have been detected in wood submerged over a year.