74 ELEMENTS OF BOTANY 
mentioned (Sect. 63), and count the rings of wood above and below 
each ring of scars. 
How do the numbers correspond? What does this indicate? 
Count the rings of wood on the cut-off ends of large billets of 
some of the following woods: locust, chestnut, sycamore, oak, hickory. 
Do the successive rings of the same tree agree in thickness ? 
Why? or why not? 
Does the thickness of the rings appear uniform all the way round 
the stick of wood? If not, the reason in the case of an upright 
stem (trunk) is perhaps that there was a greater spread of leaves on 
the side where the rings are thickest or because there was unequal 
pressure caused by bending before the wind. 
Do the rings of any one kind of tree agree in thickness with those 
of all the other kinds? What does this show? 
Tn all the woods examined look for: 
(a) Contrasts in color between the heartwood and the sapwood.? 
(b) The narrow lines running, in very young stems, pretty straight 
from pith to bark, in older wood extending only a little of the way 
from center to bark, the meduliary rays shown in Fig. 42.2 
(c) The wedge-shaped masses of wood between these. 
(d) The pores which are so grouped as to mark the divisions 
between successive rings. These pores indicate the cross-sections of 
vessels or ducts. Note the distribution of the vessels in the rings to 
which they belong; compare this with Fig. 45 and decide at what 
season of the year the largest ducts are mainly produced. Make a 
careful drawing of the end-section of one billet of wood, natural 
size. 
Cut off a grapevine several years old and notice the great size of 
the vessels. Examine the smoothly planed surface of a billet of red 
oak that has been split through the middle of the tree, and note the 
large shining plates formed by the medullary rays. 
Look at another stick that has been planed away from the out- 
side until a good-sized flat surface is shown, and see how the medul- 
lary rays are here represented only by their edges. 
1 This is admirably shown in red cedar, black waluut, barberry, black 
locust, and osage orange. ‘ 
2 These and many other important things are admirably shown in the thin 
wood-sections furnished for $4 per set of 24 by R. B. Hough, Lowville, N.Y. 
