Wood

• Outer bark

  Provides mechanical protection to the softer inner bark and also helps to limit evaporative water loss
• Inner bark

  The tissue through which sugars (food) produced by photosynthesis are translocated from the leaves to the roots or growing portions of the tree
• Cambium

  The layer between the bark and the wood that produces both these tissues each year
• Sapwood

  The active, "living" wood that conducts the water (or sap) from the roots to the leaves
• Heartwood

  The wood extending from the pith to the sapwood
• Pith

  The small, soft core occurring near the center of a tree trunk
• Medullary rays

  Sheets or ribbons of cells running from the inside of the plant to the outside
• Endogenous

  Tree that grows by the addition of new material inwards
• Exogenous

  Tree that grows by the addition of new wood outwards, immediately under the bark
• Hardwood

  • Trunk divides to develop large branches, have branches that are larger and irregular, have broad leaves, are slow growing, valuable, harder and more durable
• Softwood

  • Have straight trunk, smaller branches, needle-like leaves, symmetrical in shape, grow quickly, cheaper, softer and less durable
• Interlocked‑grained wood

  Wood in which the fibers put on for several years may slope in a right‑handed direction, and then for a number of years the slope reverses to a left‑handed direction, and later changes back to a right‑handed pitch, and so on
• Diagonal‑grained wood

  Wood in which the annual rings are at an angle with the axis of a piece as a result of sawing at an angle with the bark of the tree or log
• Spiral‑grained wood

  Wood in which the fibers take a spiral course about the trunk of a tree instead of the normal vertical course
• Straight‑grained wood

  Wood in which the fibers run parallel to the axis of a piece
• Wavy‑grained wood

  Wood in which the fibers collectively take the form of waves or undulations
• Knot


  That portion of a branch or limb that has been surrounded by subsequent growth of the stem
• Shake

  A separation along the grain, the greater part of which occurs between the rings of annual growth
• Check

  Separation of the wood that normally occur across or through the annual rings
• Split

  Separation of the wood through the piece to the opposite surface or to an adjoining surface caused by tearing apart of the wood cells
• Bow

  Distortion of lumber in which there is a deviation, in a direction perpendicular to the flat face, from a straight line from end-to-end of the piece
• Crook

  Distortion of lumber in which there is a deviation, in a direction perpendicular to the edge, from a straight line from end-to-end of the piece
• Cup

  Distortion of a board in which there is a deviation flatwise from a straight line across the width of the board
• Wane

  Bark or lack of wood from any cause on edge or corner of a piece except for eased edges
• Torn grain

  Result of heavy tools or things dropped accidentally on the finished surface which led to a small depression
• Chip mark

  When the timber is cut through the planning machine, the parts of the machine may form chip marks on it
• Dry rot

  Any dry, crumbly rot but especially to that which, when in an advanced stage, permits the wood to be crushed easily to a dry powder
• Wet rot

  Caused by fungi that decompose the timber and convert it into a grayish-brown powder form
• Heart rot

  Generated in the trees when fungi attack the heartwood through its newly formed branch
• Sap stain

  When the moisture content in the timber is more than 25%, some types of fungi attack the sapwood and make it discolored
• Plain sawn lumber

  Lumber that has been sawn parallel to the pith and approximately tangent to the growth rings
• Quarter sawn lumber

  Lumber that has been sawed so that the wide surfaces extend approximately at right angles to the annual growth rings
• Seasoning

  Removing moisture from green wood to improve its serviceability
• Defect

  Any irregularity occurring in or on the timber which may lower its strength, durability, utility value or diminish its appearance
• Wood

  Fibrous substance which composes the trunk and branches of a tree that lies between the pith and the bark
• Structure of Wood

  1. Outer Bark

  2. Inner Bark

  3. Cambium

  4. Sapwood

  5. Heartwood

  6. Pith

  7. Medullary Rays
• Class. of wood according to mode of growth

  1. Endogenous

  2. Exogenous
• Class. of wood according to density

  1. Hardwood

  2. Softwood
• Class. of wood according to grains

  1. Interlocked-grained wood

  2. Diagonal-grained wood

  3. Spiral-grained wood

  4. Straight-grained wood

  5. Wavy-grained wood
• Def. in lumber due to abnormal growth

  1. Knot

  2. Shake