Vegetable Staticks. 147 



Another argument for the circulation of 

 the fap, is that fome forts of graffs will 

 infect and canker the flocks they are grafted 

 on : But by Exper. 12, and 37, where mer- 

 curial gages were fixed to frefh cut flems of 

 trees, it is evident that thofe ferns were 

 in a ftrongly imbibing flate ; and confe- 

 quently the cankered flocks might very like- 

 ly draw fap from the graft, as well as the 

 grafF alternately from the flock; juft in the 

 fame manner as leaves and branches do 

 from each other, in the viciffitudes of day 

 and night. And this imbibing power of 

 the flock is fo great, where only fome of 

 the branches of a tree are grafted, that the 

 remaining branches of the flock will, by 

 their flrong attraction, flarve thofe graffs; 

 for which reafon it is ufual to cut off the 

 greateft part of the branches of the flock, 

 leaving only a few fmall ones to draw up 

 the fap. See. Vol. II. p. 265. 



The inflance of the Ilex grafted upon the 

 Englijh Oak, feems to afford a very confix 

 derable argument againfl a circulation. For, 

 if there were a free uniform circulation of 

 the fap thro' the Oak and Ilex, why fhould 

 the leaves of the Oak fall in winter, and not 

 thofe of the Ilex? 



L 2 Another 



