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when the Sap firft begins to move, fo as to make the 

 bark run, and eafily peel off, he believes it would be 

 found, that the lower bark is firft moiftened, whereas 

 the bark of the top branches ought firft to be moiften- 

 ed, if the Sap defcends by the bark. As to the Vine, 



he fays, he is pretty well afTured, that the lower bark 

 is firft moiftened. 



He adds, That it is to be feen in many of the exam- 

 amples of the experiments he has given in that book, 

 what quantities of moifture trees daily imbibe and 

 perrpire ; now the celerity of the Sap muft be very 

 ■ great, if that quantity of moifture muft moft of it 

 • afcend to the top of the tree, then defcend, andafcend 

 ^gain, before it is carried off by perfpiration. 

 Thedefeftof a circulation in vegetables feems, in 

 .... fome meafure, to be fupplied by the much c^reater 

 ■ quantity of liquor which the vegetable takes in, than 

 \ the animal, whereby its motion is accelerated ; for, 

 , by the firft example he gfves, we find the Sunflower, 

 bulk for bulk, imbibes and perfpires feventeen times 

 . more frefti liquor than a man every twenty-four hours. 

 , Befides, nature's great aim in vegetables being only 

 .that the vegetable life be carried on and maintained, 

 . there was no occafion to give its Sap the rapid motion 

 which-was necelTary for the blood of animals. • 

 In animals it is the heart which fets the blood in mo- 

 tion, and makes it continually circulate, but in vege- 

 . tables we can difcover no other caufe of the Sap's mo- 

 tion, but the ftrong attraction of the capillary Sap- 

 veflels, afTifted by the brifk undulation aiid vibrations 

 caufed by the fun's warmth, whereby the Sap is car- 

 ried up to the top of the talleft trees, and is there per- 

 fpired off through the leaves ; but, when the furface 

 of the tree is greatly diminifhed by the lofs of its 

 leaves, then alfo the perfpiration and motion of the 

 *: Sap is jproportion^bly diminifhed, as Is plain flrom 

 ' many of his experiments. ^^ i;r - 



So that the afcending velocity of the Sap is princi- 

 pally accelerated by the plentiful perfpiration of the 

 ; leaves, thereby making room for the fine capillary- 

 .' veflels to exert their vaftly attrafting power; which 

 ; I)erfpiration is efftaed by the brifk rarefying vibra- 

 . tions of warmth, a power that does not feem to be 

 ; any ways well adapted to make the Sap defcend from 



. the tops of vegetables, by different vcfTels, to the 

 " root." ^ ^ ''^ ^ . : 



If the Sap circulated, it muft needs have been feen 

 ^ defcending from the upper part of large gafties cut in 

 ■^branches fet in water, and with columns of water 

 ^.prefTing on their bottoms in long glafs tubes, In his 



43d and 44th experiment, 

 , In both which cafes it is certain that great quantities 

 of water paffed through the Item, fo that it muft 

 Ineeds have been (ttxi defcending, if the return of the 

 Sap downward were by rrufion bi" pulfion,'wT[iereby 

 , the blood in animals is returned through the veins to 

 the heart, and that pulfipn, if there were any, muft 

 Tieceffarily be exerted with prodigious force to be able 

 to drive the Sap through the finer capillaries..' 

 So that if there be a return of the Sap downward, it 

 ,, muft be by attraction, and that 'a very powerful one, 

 as may be feen by many of thefe experiments, andpar- 

 . ticularly by experiment the i ith. But it is hard to 

 conceive what and where that power is, wfiich can be 

 ; equivalent to that provifion nature has made for tlie 

 afcent of the Sap, in cgnfeguen^e of the great perfpi 

 ration of the leaves. . . : 



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tree, have been looked upon as proofs of the circu- 



Jation of the Sap, becaufe their branches, which were 



far below the inoculated bud, were gilded.' But we 



have many vifible proofs in the Vine, arid otKer 



bleeding trees, of the Sap's receding back, andpufh- 



ing forward alternately, at different times of the day 



and night ; and thfere is great reafon to think that the 



Sap of all other trees, has fuch an alternate receding 



and progreffive motion, occafioned by the alternacies 



^ of day and night, warm and cold, moiftanddry. 



' For the Sap in all vegetables does' probably recede, 



; m fome meafure, from the tops of branches, as the 



fun leaves tiiem, becaufe its rarefying power ttienl 

 ceafing, the greatly rarefied Sap and air mixed with 

 It will condenfe, and take up Ids room than they did 

 and the dew and rain will then be ftrongly imbibed 

 by the leaves, as is probable from experiment 42, and 

 feveral others, whereby the body and branches of the 

 vegetable, which have been much exhaufted by the 

 great evaporation of the day, may at night imbibe Sap 

 and dew from the leaves. 



For, by feveral experiments in the ift chapter of the 

 afore faid book of Vegetable Statics, plants were 

 found to increafe confiderably in weight in dewy and 

 moift nights, . ."■ 



And by other experiments on the Vine, in the 3d 

 chapter, it was found that the trunk and branches of 

 Vines were always in an imbibing ftate caufed by the 

 • great perfpiration of the leaves, except in the bleeding 

 feafon j but, when at night that perfpiring power 

 ceafes, then the contrary imbibing power will prevail, 

 and draw the Sap and dew from the leaves, as well 



, as moifture from the roots. 



And we have afurther proof of this in experiment 12, 



where, by fixing mercurial gauges to the ftems of 



feveral trees which do not bleed, it is found that they 



are always in a ftrongly imbibing ftate, by drawing 



up the mercury feveral inches ; whence it is eafy to 



conceive, how fome of the particles of the gilded bud 



in the inoculated Jafmine my be abforbcd by it, and 



thereby communicate their gilding miafma to the 



Sap of the branches, efpecially when, fome months 



after the inoculation, the ftock of the inoculated Jaf- 



, mine is cut off a little above the biid', whereby the ftock, 



■ which was the counter-afting part of the ftem,* 'being 



, taken away, tKe ftem attradts more vigoroufly from 



the bud. 



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Anotherargumentfor the circulation of the Sap is, 

 that fome forts dt grafts will infe6t and canker the 

 ftocks they are grafted on, but by experiment xz 

 and 0^^^ where mercurial gauges were fixed to frefh- 

 cut ftems of trees, it is evident that thofe ftems 

 were in a ftrongly imbibing ftate, and confequently 

 the cankered ftocks might very likely draw Sap from 

 the graft, as well as the graft alternately from the 

 ftock, juft in the fame manner as leaves and branches 

 do from each other in the vicifficudes of day and 

 night. ^ ^ _ \ - 



And this imbibing power of the ftock is fo greats 

 .^^ where only foniepf the branches of the ftock will, by 

 ^': tlieir ftrong attraftipn, ftarve thofe grafts, for which ' 

 'reafon It is ufual to cut off the gfeateft part of the 



., branches of the ftock, leaving , only a few fmallones 

 ^ao draw up the Sap^" ':^;:^^.-^:;-,. 



. The inftance of the Ilex grafted upon the Englifh Oak 

 feems to afford a very confiderable argument againft 

 a circulation, for if there were a free uniform circu- 

 lation of the Sap through the Oak and Ilex, why 



, Ihould the leaves of the Oak fall in winter, and not 

 thofe of the Ilex ? , -^ ,.; 



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Another argument' againft an uniform circulation of 

 the Sap in trees, as in animals, may be drawn from 

 Dr. Hale's 3 7th experiment, viz. where it was found, 

 by the three mercurial gauges fixed to the fame Vine, 

 that while fome of its branches changed their ftate of 

 protruding Sap into a ftate of imbibing, others conti- 

 nued protruding Sap, one nine,^ and the other thir- 

 teen days longer, . .; • - ..% :, -^^- '., '^ 

 •That the Sap does not defcend, between the bark and 

 the wood, as the favourers of a circulation fuppoie, 

 feerns evident from hence, viz. That if the bark be 

 taken off for three or four inches breadth quite round, 

 the bleeding of the tree above that bared place will 

 much abate, which ought to have the contrary effeft, , 

 by intercepting the courfe of the refluent Sap, if the 

 Sap defcended by the bark. 



But the reafon of the abatement of the bleeding in 

 this cafe may be vrell accounted for, from the mani- 

 feft proof we have in thefe experiments, that the Sap 

 is ftrongly attracted upward by the vigorous opera- 

 tion of the perfpiring leaves, and attracting capilla- 

 ries 5 but, when the bark is cut off for fome breadth 



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