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rauli, Mariotte, and Malpighi. Ii has met, how?- ■ it to the farina or dud in the apices, whicii is 



ver, wlch Tome confidcrable oppofcrs, particularly 

 the exccllerit M. Dodart, who could never be recon- 

 ciled to it. 



One of tlie great arguments for it is, That the fame 

 txpcrimcnts (;f ligature and incifion, which evince a 

 circulation of the blood in animals, fucceed in 

 like manner in plants, particularly in fuch as abound 

 with a milky fap, as the Great Tithymale, Milk- 



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rhiltle, &c. if the ligature be Uftened tight round 

 them, the part above is found to fwell very confide- 

 rably, and that below it a little, whence it appears, 

 that there is a juice defcending from the branches, and 

 that the latter is thicker than the former, which qua- 

 drates exactly with the common fyftem, the juice be- 

 ino; fuppofed to arife in capillary- veiTels, in form of a 

 iubcile vapour, which condenfed in the extremes of 

 the plant by the neighbourhood of the cold air, turns 

 back in form of a liquor through the more patent 

 pipes of the inner bark. 



M. Dodart, inftead of the fame juice's going and re- 

 turning, contends for two feveral juices, the one im- 

 bibed from the foil digefted in the root, and from 

 thence tranfmitting from the extremes of the branches 

 for the nouriftiing of the plant, the other received 

 from moifture of the air entering in at the extremities 

 of the branches and furfaces of the leaves, fo that the 

 afcending and defcending juices are not the fame. 

 One of his chief arguments is, That if two trees of 

 the fame kind be tranfplanted in one day, after firft 

 cutting off their roots and branches; and if, after 

 they have taken root, fome of the new fhoots put 

 forth each year be cut off one of from them, it will 

 not thrive half fo well, notwithftandino; its root and 

 trunk being entire as the other. 

 This he conceives to be a proof of the plant's deriv- 

 ing nourifliment by the branches, and concludes it to 

 be of an aerial nature, becaufe formed of the moifture 

 of the air, dew, &c. whereas that imbibed from foil 

 is terreftrial, &c. Hift. de TAcad. Roy. Ann. 1709. 

 But by this experiment we can only reafon for the I . For by the expanfion of the trachea, the vefTcls con- 



to 





were, the male feed of the plant, whrre having uar.cr- 

 gone a further maturation, it is Ihed into x.1^ pji\ii 

 v/hich performs the office of an uterus or wo:nb, a-.d 

 thus having acquired its lafl perfedion, ic dvcs rife 

 to a new fruit or plant. 



The root or part, wlicreby vegetables are connefted 

 to their matrix, and by which they receive their nu- 

 tritious juice, confifts of an infinite number of abforb- 

 ingvcfTels, which, being difperlcd through the inter- 

 dices of the earth, attract or imbibe the juices of tlic 

 fame. Confequently, every thing in the earth that 

 is difToluble in water, is liable to be imbibed, as air' 

 fait, oil, fumes of minerals, metals, &c. and of thefc 

 plants really confift. 



Thefe juices are drawn from the earth very crude 

 but by the ftrufture and fabric of the plant, and 

 the various veflels they are ftrained through, become 

 changed, further elaborated, fecreted, and affimilared 

 to the fubftance of the plant. 



The motion of the nutritious juices of vegetables is 

 produced much like that of the blood in animals, by 

 the action of the air; in effeft, there is fomethino- 

 equivalent to refpiration throughout the whole plant! 

 The difcovery of this is owing to the admirable Mal- 

 pighi, who firft obferved, that vegetables confift of 

 two feries or orders of veffels : 



1. Such as receive and convey the alimental juices, 

 anfwering to the arteries, ladeals, veins, &c. of ani- 

 mals. 



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2. Trachese or air- veffels, which are long hollow pipes, 

 wherein air is continually received and expelled, i. ^. 

 infpired and expired; within which tracheal he 

 fhews all the former feries of veffels are contained. 

 Hence it follows, that the heat of a year, nay, of a 

 day, of afingle hour, or minute, muft have an ef- 

 fcd: on the air included in thefe trachea?, i, e. muft 



i rarefy it, and confequently dilate the tracheae, whence 

 ^arifes a perpetual ipring or fource of aftion to pro- 

 mote the circulation in plants. 





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trees fo cut, that a great part of the increafmg Sap is 

 deftroycd, 'which was contained; in thefe 



taining the juices arepreffed, and by that means thc^ 



branches, whereby the trees were deprived of this Sap, 

 fo'could hot make fo great progrefs. 



young juice contained is continually propelled, andfoaccc- 



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lerate^, by which propulfion the juice is continually 

 ;Com minuted, and rendered more and more fubtile, 

 'The humour or Sap of a plant, then. Is a juice fur- I .and fo enabled to enter veffels ftill finer and finer, the 

 niftied by the earth, and changed into the plant, con- 1 • ^thickeft part of it being at the fame time fecreted and 

 fifting of fome foffil parts, other parts derived from I depofited into the lateral cells or loculi of the bark 

 the air and rain, and others from putrefied animals, to defend the plant from cold, and other external 



plants, &c. Confequently, in vegetables are contained 

 all kinds of falts, oil, water, earth, &c. and probably 

 all kinds of metals too, inafmuch as the afties of ve- 



injunes. 



The juice having thus gone its ftage from the root to 



the remote branches, and even the flower, and hav- 



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getables always yield fomewhat which the loadftone I ing, in every part of its progrefs, depofited fome- 

 attrafts. J thing both for aliment and defence, what is redun- 



This juice enters the plant in form of a fine and fub- dant paffes out into the bark, the veffels whereof are 

 tile water ; which, the nearer it is to the root, the J inofculated with thofe wherein the Sap is mounted, 



and through thefe it re-defcends to the root, and 

 then to the earth again, and thus a circulation is 



more it retains of its proper nature, and the farther 

 from the root, the more a6tion it has fuftained, and 





the nearer it approaches to the nature of the vegetable. 

 Confequently, when the juice enters the root, the 

 bark whereof is furniftied with excretory veffels, fitted 

 - to difcharge the excrementitiouspart, it is earthy, wa- 

 tery, poor, acid, and fcarce oleagmous at all. 

 In the trunk and branches it is further prepared, tho' 

 it ftill continues acid, as we fee by tapping or perfo- 

 rating of a tree in the month of February, when it 

 '^ diftils a watery juice apparently acid. - - 



;- The juice, being here carried to the germs or buds, 

 >^- is more concoi5ted ; and here, having unfolded the 

 - leaves, thefe come to ferve as lungs for the circula- 

 -( tion and further preparation of the juice, 

 •t^ For thefe tender leaves, being expofed to the alter- 

 -^^ nat'e adion of heat and cold, moift nights, and hot 

 fcorching days, are alternately expanded and con- 

 tracted, and the more on account of their reticular 

 ' texture, i 



■' By fuch means is the juice ftill further altered and di- 



. gefted, as it is further in the petala or leaves of the 



■ flowers which tranfmit the juice, now brought to a 



greater fubDlty,^ to the ftamina ; thefe communicate 



effected. 



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Thus is every vegetable a£ted on by heat and cold, 

 during the day time efpecially, while the fun's force 

 is confidcrable, the Sap-veffels fqueezed and preffed, 

 and the Sap protruded and raifed, and at length eva- 

 cuated, and the veffels exhaufted ; and in the night 

 again, the fame tracheae being contracted by the cole! 

 the air, the other veffels are eafed and relaxed, anc 

 fo difpofed to receive frefh food for the next day's 

 digeftion and excretion. 



Whatcourfe the juice takes after it is imbibed by 

 the roots is not very clear. The veffels that take it 

 up, to convey to the plant, are too fine to be traced, 

 and hence it has been controverted, whether it is by 

 the bark, or th^ pith, or the woody part, that the 



plant is fed. 



The more common opinion is for the bark, 

 juice, raifed by the capillaries of the wood, is^ here 

 fuppofed to defcend by the larger fibres, placed, in the 

 inm-oft part thereof, immediately over the wood, in 

 which defcent, the Sap, now fufficiently prepared, 

 adds a part of its fubftance to the contiguous wood 



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