The BAP in TREES. 21 



ceffively, upon the lower fide of all the other incifions, mark- 

 ed i, and flowed plentifully, while the upper fide of all the 

 feven incifions, marked k, remained dry. 



COR. 15. The refult of thefe trials then amounts to this: That 

 there was at prefent no defcending fap from the branches : 

 That the whole fap of the tree was in an afcending flate : That 

 it had now reached about nine feet high in the trunk j be- 

 yond which height it was flill dry, and refufed to bleed. 

 BEING aflured of this, I now applied myfelf to examine an 

 experiment of M. DU HA MEL, upon which he founds his doc- 

 trine of a defcending fap in the bleeding feafon. 

 EXP. 9. This experiment was made, by fawing two inches deep 

 into the tree, at L, one foot from the ground. - Another inci- 

 fion, of the fame depth, was made three inches below, both 

 being horizontal j and the wood and bark between the two 

 were completely extracted. The fap was then perceived to 

 flow as plentifully from the furface of the upper incifion at 

 m, as from that of the under incifion at n. 

 COR. 1 6. From this experiment, M. DU HAMEL* fuppofes, that, 

 in the bleeding feafon, there is not only an afcending but a 

 defcending fap. Finding the fap to iflue from both incifions, 

 he concludes, that it moves at the time in two different 

 directions, or both upwards and downwards. The facts 

 which he delivers in the above, and in other experiments, 

 which I alfo repeated, are certainly true ; but this conclufion 

 which he draws from them is xinqueftionably erroneous. 

 IT is evident, from the whole train of our experiment, that r 

 from the earlieft fpring to the prefent day, the 28th of March, 

 all the fap which flowed in the birch was in an afcendmg 

 flate, and that there was no defcending fap whatever from 

 the extremities of the tree towards the root. But when 

 once any part of a tree comes to be replete with this afcend- 



* Phyfique des Arbres, torn. i. p. 66. 



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