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And accordingly he obfervcs, that the Leaves next 1 clofet, where the air was very temperate i and as the 

 adjoining to the bloflbms are in the fpring very much ' ' ' "" 



expanded, when the other Leaves on barren fhoots 

 are but beginning to fhoot, and that all Peach Leaves 



one- 



are very large before the bloffom goes off. 

 And that, in Apples and Pears, the Leaves 

 third or half grown, before the bloffom opens, fo pro- 

 vident is nature in making timely provifion for the 

 nourifhing the yet embryo fruit. 

 He a)fo adds another experiment : he ftripped the 

 Leaves of an Apple-tree branch, and then fixed the 

 great end of the ftem in the gage, it raifed the mer- 

 cury 2+4- inches, but it foon fubfided, for want of 

 the plentiful perfpiration of the Leaves, fo that the 

 air came in almoft as faft as the branch imbibed 



water. - . 



And as a farther proof of the influence of the Leaves 



. in raifmg the fap, he alfo made the follov;ing expe- 

 riment. 

 On the fixth of Augufl, he cut off a large Ruffct 



. Pippin, with a ftalk i 4- -iifichlong, and twelve ad- 



. joining Leaves growing to it. . . 



He cemented the ftalk fall in the upper end of a 

 tube, which tube was fix inches long,' and oJie- 

 fourtb diameter i as the ftalk imbibed the water, it 



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raifed the mercury four inches high. 

 That he fixed another Apple of the fame fize in the ' 

 fame manner, but firft pulled off the Leaves, and it 

 raifed the mercury but one inch j that in the fame , 

 xnanner he fixed a like-bearing twig, with twelve 

 Leaves on it, but no Apple, and it raifed the mercury 

 three inches. ':^ sj. .> :, / 



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He then took a like-bearing twig, without either 

 Leaves or ^ Apple, and it railed the mercury one- 

 /. fourth of an inch. ..'>: . 



T ^ _ _ _ Jm 



f^r:,So a twig, with an Apple and Leaves, raifed the 

 hiercury four inches •, one with Leaves, only three 

 .VX- inches J one with an Apple without Leaves, only one 



..>r, inch. _ . ' 



c * A Quince, which had two Leaves juft at the twig's 

 ,:'j infertion, raifed the mercury 2 4- 4- inches, and held 

 it up a confiderable time. 

 )i;, A fprig of Mint, fixed in the fame manner, raifed 

 the mercury 3+4- inches, = to 4 fc^t 5 inches 

 -y; height of water. - . ' 



Thefe, and many more experiments of the Rev. Dr. 

 <>r:j: Hales, that curious enquirer into the caufes, ftate, 

 , *i*>ti*j&d progr^fs of vegetation, evidently fhevy the great 

 ,c^n- perfpiration of the Leaves of plants, and their great 

 .,ro life in raifing the fap, and other functions of vegeta- 

 ..V ble nature; to whofe excellent treatife before-men- 

 r ,. £ tipned, I refer the curious enquirer. ,., 



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>::! ^IhalUdd, Xhat mm^ ha,s ^^irf(5l:e4..u§ . as to the 



:^true diftancewe oug-ht to train the branches of trees 



againft walls or efpaliers, which fhould alwaiys be in 



proportion to the lize of their Leaves ; for if we re- 



gard her progrefs in the great varieties of trees, which 



^ nsl are wkhiii o,ur,obfqryation,, la^e, fbajl. always find their 



fH / branches o;row diftant from each other in proportion 



r. i, to the breadth of their Leaves ; and it was upon this 



x .account that the Romans fo mucH admired the Plata- 



';: ixf nysj, l;>ecaufe the Leaves, being large, afforded them 



•-'*ar a kmdly fhadgin fumnjer, but in winter, \y hen they 



;>i/are deftitute of Leaves, their branches growins; at a 



great diftance, eafily admitted the beams of the fun. ^ 



X fh^l next beg leave to mention a few, out of the 



:i many experiments which hdve been made by Monf. 



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Bonnet, of Geneva, to prove that moft Leaves im- 

 % bibe the moifture of the air on their under furface, 

 : p,m not from their upper : they are as follow : 

 : xie gathered the Leaves of fixteen Xorts of herba- 

 r ceou^ plahts when fully grown j of each he put fcveral 

 ' l^^^y.fs ypon the fuiface of water in glafs vafes, fome 

 . "Were pofited with their upper furface, and others with 

 ; their under furface upon the Water,; theje were ad- 



jufted exadlly to the furface of the water, with great 

 ' care not to let any nK)ifture reagli their oppofite fur- 

 i, faces, and the fame care was taTcen to prevent their 



foot-ftalks from recj^iyiflg.any moiftiire... The glaffeS 



m which thefe Leaves were thus placed, were kept in a 



or 



o 



water in the glaffes evaporated, there was from time 

 to time a fupply of frelh, which was added with a 

 fyringe, fo tliat the Leaves were not difturbed. The 

 Leaves were taken from the following plants ; the 

 Plantain, the Mullein, the Wake Robin, the great 

 Mallow, the Nettle, the Marvel of Peru, the Kindney- 

 bean, the Sun-flov/er, the Cabbage, the Balm, the 

 Cock's-comb, the purple-leaved Amaranth, Spinach, 

 and the fmaller Mallow. 



Six of thefe forts he found continued green a Ion 

 time, and thefe were with different furfaces upon the 

 water ; they were of the following forts, the Wake 

 Robin, the Kidney-bean, the Sun-flower, the Cab- 

 bage, the Spinach, and fmall Mallow; among the 

 others the following forts were found to draw the 

 moifture better with their upper furface than their 

 under, the Plantain, the Mullein, the great Mai- 

 low, the Nettle, the Cock's-comb, and the purple 

 Amaranth. 



The Leaves of the Nettle whofe "under furface was 



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upon the water, were decayed in three weeks, whereas 

 - thofe whofe upper flirface was next the water conti- 

 nued two months. , : ' . . 



TJie Leaves of Mullein, whofe under furface w^as 

 next the water, did not continue frefh more than five 



.;: .jQT fix days, but thofc whofe upper furface was next 



, the ^ater lafted five weeks. 



. .The Leaves of the purple Amaranth, whofe upper 

 furface was next the water, continued frefli three 

 . months, whereas thofe whofe under furface was next 

 . the water, were decayed in a week. ;^ ;. 

 The Leaves of the Marvel of Peru and the Balm, 

 appeared to have the advantage, whofe under fur- 

 faces were next the water. ' ' vv-/ "i-"' 

 The Leaves of Wake Robin and of the Cock's- 

 comb, whofe fcot-ftalks only v/ere put into the wa- 

 ter, continued frefli a longer time than thofe which 

 were placed with either furface next the water. 

 The Leaves of the Great Mallow, the Nettle, the 

 Sun-flower, the Marvel of Peru, and Spinach, whofe 

 foot-ftalks were plunged into the water, continued 

 frefti a Ihorter time than thofe which had either of 

 their furfaces next the water. 



The Leaves of the Mullein, of Plantain, and Ama- 

 ranth, -which received the water at their foct-ftalk, 

 continued frefti much longer than thofe, whofe under 

 furface was next the water. - . ' . - 



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. Jt is not difficult to explain the reafon of this faft, 



for the orifices of the fap-veffels in the foot-ftalk, 



are much larger than thofe of either furface, fo that 



the moifture infinuafes in greater quantities', and with 



more eafe, the firft than by t,he fecond wav. ' 



-, After this the mme eentleman made experiments on 



\the Leaves of fixteen forts of trees and fhrubs of 



the following fbrts^ the Lilac, the Pear-tree;, the 



Vine, the Alpen, the Laurel, the Cherry-tree, the 



Plumb-tree, the Horfe .Chefnut, the .White. Mul- 



berry, the Lime-tree, the Poplar, the 'Apricot, the 



Walnut, the Filbert, the Oak, and the Creeper. 



.Among thefe fpecies, he found that the Lilac and 



the Afpen imbibed the moifture on their upper fur- 



,Tace, equally with the under furface j but in all the 



' other forts, the under furface imbibed It in much 



greater quantities than the oppofite. The difference 



.'was very remarkable in the Leaves of tfie White 



■jMulberry, for' thofe whofe iippier furfacfe wds laid 



. upon the water, faded in fivp.days, wherea^ the other 



- whofe under furface was next the water, preferved 



. . their verdure near fix months. >;.- 



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' . The Vine, the Poplar, and Walnut-tree are very re- 

 , markable inftances, how litl!e difpofed the upper fur- 

 faces of the Leaves of ligneous plants are to imbibe 

 the moifture ; fqr thofe of thefe three forts, whofe 

 vppcr furfaces were applied to the water, decayed al- 

 moft as foop as thofe which had no ncurifliment. 

 In all the experiments made ty this curious gentleman 

 upon the various Leaves of trees and herbs, it is re- 

 v-markable," that all thofe Leaves which imbibed the 



moifture by their upper furfac^, were^ jfuch as had 



.'■■.' ■■ " -^ . --'-^•.'^..f^*^^^-* that 



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