DENDROLOGY WOOD ANATOMY LAB I


I.  Make freehand transverse sections midway between successive bud scale scars on one
of the three year Tilia twigs you collected.  Examine these sections in developmental
sequence using a binocular dissecting microscope.  Note the transverse relationships
between successive annual growth rings in each section.  Identify as many tissues as you
can in your sections.

II.  Obtain a compound light microscope and learn how to establish Kohler illumination.  This
procedure, named after August Kohler who developed the theory and procedure in 1894,
should be preliminary to each exercise involving the compound light microscope in order
to optimize resolution and avoid eye strain.

1.  Make sure a) ocular, b) objective, and c) condenser lens are clean.

2.  Put the 10X objective in the viewing position.

3.  Adjust interpupillary distance of oculars.

4.  Place a prepared slide on the microscope stage.

5.  Bring the image of the prepared slide into sharp focus.

6.  Open condenser iris diaphragm.

7.  Put the fake lamp diaphragm over half the lamp housing.

8.  Focus the image of the edge of the fake lamp diaphragm.

9.  Remove the fake lamp diaphragm.

10.  Remove one ocular.

11.  Peer down the ocular tube and adjust the condenser diaphragm so that ca. 80% of the
objective lens is illuminated.

12.  Replace ocular.

13.  Adjust the lamp voltage control for comfortable viewing.

NOTE:  When the objective lens is changed it is necessary to adjust the condenser
diaphragm to 80% illumination as in steps 10-13.  You will use small strips of time tape to
mark the appropriate condenser diaphragm positions to facilitate these adjustments.  Also
use a piece of time tape to place your initials on the microscope you will be using each
laboratory.
III.  Study in chronological sequence the prepared light microscope cross sections of the 1,
2, and 3 year old Tilia stems.  Relate your observations to what you observed in your
freehand sections.  Identify:  annual rings, pith, primary and secondary xylem, ray
parenchyma, cambium, primary and secondary phloem, dilated ray parenchyma, cortex,
phellum (cork), phellogen (cork cambium), phelloderm.  Note if there are any lenticels
present.

IV.  Make a freehand longitudinal section of the other Tilia twig you collected.  Section
through the pith throughout three years of stem growth.  Examine your section using a
binocular dissecting microscope.  Note the longitudinal relationships between the
successive annual growth rings.  Relate these to your transverse observations in I. and III.
above.