PLANTS. 
13 
water pressing on their bottoms in long glass tubes. 
In both which cases, it is certain that great quan- 
tities of water passed through the stem, so that it 
must needs have been seen descending, if the return 
of the sap downwards were by trusion or pulsion, 
whereby the blood of animals is returned through 
the veins to the heart ; and that pulsion, if there 
were any, must necessarily be exerted with pro- 
digious force, to be able to drive the sap through the 
finer capillaries. So that, if there be a return of the 
sap downwards, it must be by attraction, and that a 
very powerful one, as we may see by many of these 
experiments. But it is hard to conceive what and 
where that power is which can be equivalent to that 
provision Nature has made for the ascent of the sap 
in consequence of the great perspiration of the 
leaves. 
“ The instances of the jessamine-tree, and of the 
passion-tree, have been looked upon as strong proofs 
of the circulation of the sap, because their branches, 
which were far below the inoculated bud, were 
gilded ; but we have many visible proofs in the 
vine, and other bleeding trees, of the sap’s receding 
back and pushing forwards alternately at different 
times of the day and night. And there is great 
reason to think that the sap of all other trees has 
such an alternate receding and progressive motion, 
occasioned by the alternacies of day and night, warm 
and cool, moist and dry. For the sap in all vege- 
tables does probably recede in some measure from 
the tops of the branches, as the sun leaves them ; 
