In Winter Woods 395 
split the seal above them and open the lenticel 
once more. And as we have seen, a closing layer 
or seal of cork has grown across all the scars whence 
last summer’s leaves have fallen. 
Preparations for repose have taken place, not 
only on the surface of the tree, but in its inner 
tissues. The fluid which, in summer, mounts 
slowly from the tiniest rootlets toward the leaves, 
is the ‘‘crude sap.’’ It is water, holding in 
solution chemical substances derived from the soil. 
In the leaves, as we remember, it is worked over 
into the ‘ 
‘ elaborated-sap’’ which builds up and 
feeds plant-tissues. And this, creeping blindly 
from cell to cell, finds its way to the tips of 
roots and branches where growth is being actively 
carried on. 
So in latter spring and summer there is a con- 
stant slow movement of fluids in the trees, first 
from the roots upward and then from the leaves 
downward. 
Though this movement is connected functionally 
with the tree’s feeding and digestion, it resembles 
the circulation of the blood in one respect. Crude 
sap, like arterial-blood, flows always through one 
set of channels, while elaborated sap, like veinous- 
blood, flows always through another. Crude sap, 
