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M. Baisse placed branches of different trees in 

 an infusion of madder, and kept them there for a long 

 time. He found in all cases, that the wood became 

 red before the bark j and that the bark began to re- 

 ceive no tinge till the whole of the wood was colour- 

 ed, and till the leaves were affected ; and that the co- 

 louring matter first appeared above, in the bark im- 

 mediately in contact with the leaves. 



Similar experiments were made by M. Bonnet, 

 and with analogous results, though not so perfectly 

 distinct as those of M. Baisse. 



Du Hamel found, that in different species of the 

 pine and other trees, when strips of bark were re- 

 moved, the upper part of the wound only emitted fluid, 

 whilst the lower part remained dry. 



This may likewise be observed in the summer 

 in fruit trees, when the bark is wounded, the alburn- 

 um remaining untouched. 



I have mentioned in the Third Lecture, that when 

 new bark is formed to supply the place of a ring- 

 that has been stripped off, it first makes its appearance 

 upon the upper edge of the wound, and spreads slow- 

 ly downwards ; and no new matter appears from be- 

 low rising upwards, if the experiment has been care- 

 fully performed. I say carefully performed ; because, if 

 any of the interior cortical layer be suffered to remain 

 communicating with the upper edge, new bark cover- 

 ed with epidermis will form below this, and appear as 

 i'f protruded upon the naked alburnum, and formed 

 within the wound j and such a circumstance would 

 give rise to erroneous conclusions, 



