LIVING PARTS OF THE STEM 109 
Examine longitudinal sections of some of the twigs, the potatoes, 
and the roots. In drawing conclusions about the channels through 
which the ink has risen (those through which the newly absorbed 
soil-water most readily tray- 
els), bear in mind the fact 
that a slow soakage of the 
red ink will take place in 
all directions, and therefore 
pay attention only to the 
strongly colored spots or 
lines. 
What conclusions can be 
drawn from this experiment 
as to the course followed by 
the sap? 
From the familiar 
facts that ordinary for- = 
est trees apparently 
flourish as well after the 
almost complete decay 
and removal of their 
heartwood, and that 
many kinds will live 
and grow for a consider- 
able time after a ring of 
bark extending all round 
the trunk has been re- 
moved, it may readily be 
—— te 
Pie tet “wt ti, 
Fic. 77.— Channels for the Movement of 
Water, upward and downward. 
The heavy black lines in roots, stems, and 
leaves show the course of the fibro-vascular 
bundles through which the principal move- 
ments of water take place. 
inferred that the crude sap in trees must rise through some 
portion of the newer layers of the wood. A tree girdled 
by the removal of a ring of sapwood promptly dies. 
118. Downward Movement of Liquids. — Most dicoty- 
ledonous stems, when stripped of a ring of bark and then 
