Introduction to Wood Anatomy II

I. Three Dimensional reconstruction of 3 types of sections can be
     used to reveal anatomical characteristics of various species
     wood
     A. Transverse (Cross, X)
          1. Sectioned perpendicular to longitudinal axis
     B. Radial Longitudinal (R)
          1. Sectioned parallel to longitudinal axis and passes
               through middle to stem/root
     C. Tangential Longitudinal (T)
          1. Sectioned parallel to longitudinal axis but does not
               pass through middle of stem/root

II. Vascular Cambium consists of two cell types
     A. Fusiform Initials
          1. Give rise to vertically elongate cells 
               a. Sieve tube elements, vessel elements,
                    tracheids, fibers, fusiform initials
     B. Ray Initials
          1. Give rise to horizontally elongate cells
               a. ray parenchyma in xylem & phloem
                    ray initials
     C. Fusiform Initials can be converted to Ray Initials
          and vice versa

III. Primary pit fields
     A. Thinner areas of primary cell wall
     B. May or may not correspond to pit location in secondary 
          cell wall

IV. Pit morphology is often a useful diagnostic taxonomic
     characteristic of timbers.

     A. Variation occurs in size and geometry of
          1. Pit canal
          2. Pit chamber
     B. Simple Pits
          1. Pit canal & chamber same size and shape
          2. Parenchyma
     C. Bordered Pits
          1. Pit canal smaller than pit chamber
          2. Pit chamber is round
          3. Pit canal is either round (circular bordered pit)
               or elliptical (elliptical bordered pit)
          4. Tracheids
          5. Vessel Elements
     D. Two adjacent pits from different cells form
          a pit pair
          1. Simple pit pair between two adjacent parenchyma cells
          2. Bordered pit pair between two adjacent tracheid
          3. Semi- or Half bordered pit pair between a parenchyma
               cell and a tracheid/vessel element
     E. Slit Pits
          1. Pit canal very elliptical
          2. Pit chamber round          
          3. Pit chamber diameter equal to minor axis of 
               of pit canal = no border
          4. Fibers
     F. Distinctly Bordered Pits
          1. Pit can very elliptical
          2. Pit chamber round
          3. Pit chamber diameter +- equal to major axis of
               pit canal
          4. Fiber-tracheids
II. Anatomical Characteristics of Secondary Xylem Cells Derived
     from Gymnosperm Cambium
     A. Parenchyma
          1. +- thin walled
          2. +- retangular
          3. Simple pits
          4. Living cytoplasm at maturity
          5. Functions include
               a. storage of food or waste material
               b. radial transport of nutrients (elements+sugar)
                & water
     B. Tracheid
          1. Thick walled (cw/lumen -> small)
          2. Elongate with slanted end walls
          3. Bordered Pits (circular or elliptical)
          4. No cytoplasm at maturity
          5. Functions include
               a. storage of waste material in heart wood
               b. vertical transport of water & elements in
                    sapwood