FOR WAGGONER’S BIOLOGY 
25 
EXERCISE 27 
A BLOCK OF OAK WOOD 
Obtain blocks of wood — oak, if possible — and cut so as to 
show cross, longitudinal, radial, and tangential sections. (See 
Waggoner, Fig. 67.) 
I. Examine a block. What was the position of the block in the 
log? Determine where the center of the log must have been with 
relation to this block. From a study of the figure in the text (see 
Waggoner, Page 129) determine what is meant by a cross or 
transverse^ a longitudinal, a radial, and a tangential section. Locate 
such sections with reference to the block which you have. 
II. Cross or Transverse Section. What are the position and 
the appearance of the medullary rays? Do all of these reach the 
center? How many sizes of rays do you find? What is the number 
of the circles of large pores? Where and when were these formed? 
When were the circles of compact wood formed? What is an 
annual ring? What is the approximate age of your specimen? 
Note whether the color of the wood is uniform. What causes the 
heartwood to be darker than the sapwoodf (See Waggoner, 
Page 128.) What is the number of the annual rings in the sap- 
wood? 
III. Radial Section. What are the appearance and the loca¬ 
tion of the rays in the radial section? Of the annual rings? Of 
the heart and sapwoods? Why is the heartwood more durable 
than sapwood? How is quarter-sawed oak cut? (See Waggoner, 
Page 130.) 
IV. Tangential Section. What is the appearance of the rays? 
Of the annual rings? What are the darker areas on this surface? 
Select an annual ring that is seen in all three sections and trace 
out the appearance in each. 
V. Make a drawing of the block which you have examined. 
