102 ACCOUNT OF SOME EXPERIMENTS ON THE 



The young shoots of the vine, when grafted on the leaf-stalk, often 

 grew to the length of nine or ten feet ; and the leaf-stalk itself, to 

 some distance below its juncture with the graft, was found in the autumn 

 to contain a considerable portion of wood, in every respect similar to 

 the alburnum in other parts of the tree. 



The formation of alburnum in the leaf-stalk seemed to point out 

 to me the. means of ascertaining the manner in which it is generated 

 in other,. instances ; and to that point my attention was in consequence 

 attracted* t Jlaving grafted leaf-stalks with shoots of the vine, I exa- 

 mined, hi tranverse 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 return- 

 ing 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 inactive ; and I could not discover 

 anything 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 man- 

 ner ; and subsequent observation soon removed all ground of doubt. 



It is well known that, in the operation of budding, the bark of a tree, 

 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 char- 

 acter of the stock in which it is inserted. The substance which is 

 called the medullary process, is clearly seen to spring from the bark, 

 and to terminate at the line of its first union with the stock. 



An examination of the manner in which wounds in trees become 

 covered, (for, properly speaking, they never can be said to heal,) affords 

 further proof, were it wanted, that the medullary processes, (as they are 

 improperly named), like every other part of the wood, are generated 

 by the bark. 



