Introduction to Wood Anatomy III
I. Variations in Tracheid Anatomy that are taxonomically useful
     A. Pit number and arrangement
          1. Uniseriate
          2. Biseriate
               a. opposite
               b. alternate
     B. Spiral thickenings
     C. Notched Borders
     D. Tori extensions
     E. Presence of Ray Tracheids
II. Variations in Parenchyma Anatomy that are taxonomically useful
     A. Presence of axillary parenchyma
     B. Presence of resin canals
          1. Number of epithelial cells
          2. Thickness of epithelial cell wall
          3. Horizontal = canal runs radially
          4. Vertical = canal runs vertically
     C. Ray Parenchyma Details
          1. Horizontal walls = walls running radially
               a. Thin compared to tracheid walls
               b. No obvious pits
               c. Abundant pits
          2. End walls = walls running vertically
               a. Abundant pits
          3. Indentures
          4. Corners thickened
          5. Presence of crystals
III. Variations in Cross Field Pits that are taxonomically useful
     Half Bordered Pit Pairs between ray parenchyma & tracheids
     A. Pinoid = no obvious borders
          1. 1-3 very large
          2. 1-6 somewhat smaller
     B. Taxodioid
          1. Very thin border
          2. Major axis of pit canal +- equal to diameter
               of pit chamber
     C. Cupressoid
          1. Fairly thick border
          2. Major axis of pit canal smaller than diameter
               of pit chamber
     D. Piceoid
          1. Very thick border
          2. Very eccentic pit canal
          3. Major axis of pit canal extents slightly beyond
               pit chamber