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was laid bare, as the first had been, and the results were simi- 

 lar. The only difference observable was, that the woody mat- 

 ter did not form so rapidly as it did in the first instance. At 

 the expiration of three more years, a second junction had 

 taken place on the pillar last laid bare. A third was now sub- 

 jected to the same experiment, the principal difference of re- 

 sults in this case being, that no leaf-bud was formed on the 

 lower lip. As soon as the third junction occurred, the fourth 

 pillar was treated as the others had been, the growths of 

 young wood becoming gradually weaker on each succeeding 

 one being the only difference. 



" Having now detailed the way this experiment was con- 

 ducted, the facts elicited enable me to deduce : 



" 1st. That every organ in an exogenous tree may be 

 thoroughly destroyed, without causing the death of the plant, 

 provided they are gradually destroyed. 



" 2nd. Exogenous plants, through their vital processes, 

 have the power of again restoring the organs so destroyed. 



" 3rd. The formative energy takes place principally above 

 the wounded portion of the stem, and the newly formed tissues 

 increase, for the most part, in a downward direction. 



" Though these results may, at first sight, appear to be 

 little more than confirmations of the old theory of wood-for- 

 mation, and even the experiment itself in some degree simi- 

 lar to others which have already been made, the latter differs 

 materially from any I know of, in the following particulars. 

 Here the main stem of the tree was operated on, and not the 

 branches only. All the organs were destroyed, including 

 pith, medullary rays, and wood. In the course of twelve 

 years the stem of a large exogenous tree, measuring four feet 

 nine inches in circumference, has been completely killed in a 

 circular ring seven inches wide, and the organs of vitality again 

 restored, without apparently affecting the health of the tree, 

 which is now, while I write (June, 1851), in full bloom. The 

 results, I conceive, rather than adding confirmation to the es- 



