28 5 
on the Descent of the Sap in^Trees. 
leaf-stalks with shoots of the vine, I examined, in transverse 
sections, the commencement and gradual formation of the wood. 
It appeared evidently to spring from the tubes which, in my 
last Paper, (to which I must refer you,) I have called the re- 
turning vessels of the leaf-stalk; and to be deposited on the 
external sides of what I have there named the central vessels, 
and on the medulla. The latter substance appeared wholly in- 
active ; and I could not discover any thing like the processes 
supposed to extend from it, in all cases, into the wood. 
The organization of the young shoot is extremely similar to 
that of the leaf-stalk, previous to the formation of wood within 
it. The same vessels extend through both ; and therefore it 
appeared extremely probable, that the wood in each would be 
generated in the same manner: and subsequent observation 
soon removed all grounds of doubt. 
It is well known that, in the operation of budding, the bark 
of trees being taken off, readily unites itself to another of the 
same or of a kindred species. An examination of the manner in 
which this union takes place, promised some further information. 
In the last summer, therefore, I inserted a great number of 
buds, which I subsequently examined, in every progressive stage 
of their union with the stock. A line of confused organization 
marks the place where the inserted bud first comes into contact 
with the wood of the stock ; between which line and the bark 
of the inserted bud, new wood regularly organized is generated. 
This wood possesses all the characteristics of that from which 
the bud was taken, without any apparent mixture whatever with 
the character of the stock in which it is inserted. The substance 
which is called the medullary process, is clearly seen to spring 
MDCCCIII. Pp 
