of the Bark of Trees. 1 o g 
maturity to perform its office of carrying up the sap, I took oft' 
the bark between these incisions ; and I abraded the surface 
of the alburnum to prevent a reproduction of it. The albur- 
num in the decorticated spaces soon became externally dry 
and lifeless ; and several incisions were then made longitu- 
dinally through it. The incisions commenced a little above, 
and extended below the decorticated spaces, so that, if the 
sap of the central vessels generated a cellular substance (as I 
concluded it would ) , that substance might come into contact 
and form a . union with the substance of the same kind 
emitted by the bark above and below. 
The experiment succeeded perfectly, and the cellular sub- 
stances generated by the central vessels, and the bark, soon 
united, and a perfect vascular bark was subsequently formed 
beneath the alburnum, and appeared perfectly to execute the 
office of that which had been taken off ; the medulla appeared 
to be wholly inactive. 
I have already observed, that the vessels, which were gene- 
rated in the cellular substance on the surface of the alburnum 
of the sycamore and the apple-tree, traversed that substance 
in almost every direction ; and the same thing appears to 
occur beneath the old bark, when united to the alburnum. 
For having attentively examined through every part of the 
spring and summer, the formation of the internal bark, and 
alburnous layer beneath it, round the bases of regenerated 
buds, which I had made to spring from smooth spaces on the 
roots and stems of trees, I found every appearance perfectly 
consistent with the preceding observations. A single shoot 
only was suffered to spring from each root and stem, and 
from the base of this, in every instance the cortical vessels 
