16 
THE FOOD OF TREES IS IMBIBED [Part II. 
With one ex¬ 
ception, trees 
imbibe from all 
parts exposed to 
moisture, and 
transpire from 
all parts ex¬ 
posed to 
drought. 
The food of 
trees imbibed 
by the surface 
of roots. 
Food of agastric 
animals imbibed 
by the surface. 
transverse circulation between the heart-wood 
and bark; and that the joint elaboration of 
these two saps is essential to the formation of 
the new annual growth in girthing. This con¬ 
sists of a new sheath of wood, deposited outside 
the last year’s growth of wood, over the entire 
surface of the stem, branches, and roots; and also 
of a new sheath of bark inside the last year’s 
bark. These opinions, in this order, will be dis¬ 
cussed in the following pages. 
With the exception stated below, trees imbibe 
from every part of them which is exposed to 
moisture, and give off (transpire) from every 
part of them which is exposed to drought. The 
root is the part which is constantly exposed to 
moisture, and which furnishes the constant sup¬ 
ply of sap to the tree. That part of the root 
which is universally believed to imbibe no mois¬ 
ture, the woody part, is the only part which 
does imbibe moisture ; and that part of the root 
which is universally believed to be the only part 
which does imbibe moisture, the unripe ends or 
fibres, is the only part which does not imbibe 
moisture. 
In fact, the mode in which food is first received 
into plants is the same as that in which it is 
received by what are called the agastric animals, 
