i 4 Evptririfatis on tie 'Courje of tit Sdp. [Book V 1 1 1 i 



c Botanifts have made many experiments to afcertain 

 the courfe of the fap. Early in the fpring, when the 

 fap begins to flow, incifions have been made in the 

 trunk and branches of trees, as^far as the pith j and, 

 in fuch cafes, it has been constantly found, that a 

 larger quantity of fap flower! from the fuperior, than 

 from the inferior margin of the incifion. This cir- 

 cumilance led to the opinion, that in the beginning of 

 the fpring, great quantities of moiftnre are abforbed 

 by trees from the atmofphere, and hence the fource 

 of the abundance of fap *. But this conclufion is 

 found to difagree with the phenomena of nature, from 

 the two following experiments. 



' i. Incifions of various heights being made in the 

 flem of feveral plants, their roots were immerfed in 

 a decoction of log-wood. The roots abforbed the 

 coloured liquor, which at length began to flow 

 from the fuperior, and not from the inferior, mar- 

 gins of the incifions ; nor had the liquor extended 

 itfelf much upwards, beyond the margin of the inci- 

 fion from which it was difcharged. 



{ 2. In the feafon wh,en the fap flows moft abun- 

 dantly, called the bleeding feafon^ a deep cut was 

 made into the branch of a growing vine, and the 

 greateft quantity of fap was difcharged from the upper 

 margin of the incifion : but a branch of the fame" 

 tree, cut in the fame manner, being inverted, the fap 

 flowed moft copioufly from the 'other margin of the 

 incifion, which of courfe was now that next the root. 

 On the other hand,* many experiments may be 

 brought to prove direftly, that, in the bleeding fea- 

 fon, the fap afcends from the roots towards the 

 branches ; the following however may fuffice. i. Early 



* Du Hamcl and others. See Phyf. des Arbres, Tom, I. p. 67. 



in 



