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 agricultu RE. 45 ing to the pith, formed by the pulp, with its veflels, and union of the lamella, or inferlignous fibres interfperfed. Plate VII. Fig. t.< C, The inner parenchyma, orace- Plate V. Fig. 3. C tions. C, Its continuation and contary, with its vefl’els, which nedtion with the rind, indeare larger than the outer one. pendent of tihe infertions. D, The core and feeds. Fig. 4. A tranfverfe feclion of the lemon. Fig. i. A piece cut off fig. i. B B B, &< The nine pulpy bags, Fig. 3. Is fig. 2. magnified. or fecond parenchyma, placed AAA,Thefmall grains or globules between the rind and the pith; with the veffels radiated from and the clufter of fmall bags, them. which contain the acid juice, Fig. 4. A longitudinal feffion of the pear, inclofed in the large ones. Ihewing a different view of the C C, The large veffels that furfame parts with thofe of fig. 1. round the pith. A, The channel, or du<5t, which D D, Two of the large bags laid runs from the top of the pear • open, (hewing the feeds, and to the bottom of the core. their connedtion with the lamellae or membranes which 2. In a Lemon, the parenchyma appears in thr.ee difform the large bags. ferent forms. The parenchyma of the rind is of a coarfe texture, being compofed of thick fibres, woven into large bladders. Thofe neared the furface contain the effential Sect. VII. Of the nature and motion of the oil of the fruit, which burlls into a flame when the Ikin is fqueezed over a candle. From this outmod parenchy- The veffels in theSap. of plants abforb moiflure from ma nine or ten infertions or lamellae are produced, which the earth, and conveyroots ft to the trunk, branches, leaves, run between as many portions of the pulp, and unite inThis juice, when it firft. enters into the root, is to one body in the centre of the fruit, which correfponds &c. to the pith in trunks or roots. At the bottom and top crude undergoes feveral changes, by means of the different of the lemon, this pith evidently joins with the rind, itconfigurations of the veflels peculiar to each part. Thus without the intervention of any lamellae. This circum- the leaves, flowers, fruit, and feed, have all fomething ftance (hows, that the pith and bark are actually con- peculiar in the ftrudlure and arrangement of their veffds, neftedin the trunk- and roots of plants, though it is dif- vjhich produces confiderable changes in the nature of the ficult to demondrate the connexion, on account of the fap. It is not known how thefe are produced: clofenefs of their texture, and the minutenefs of their but how the flomachs of animalschanges chyle from anifibres. Many veffels are difperfed through the whole of mal and vegetable fubftances, or howmake urine, faliva, bile, this parenchyma; but the larged ones dand on the inner edge of the rind, and the outer edge of the pith, jud at <bc. is fecreted from the common mafs of blood, is aS little known. The fap likewife moves in a lateral or hothe two extremities of each lamella. The fecond kind of parenchyma is placed between rizontal diredtion. the rind and the pith, is divided into didimft bodies Philofophers are greatly divided about what they call by the lamellae ; and each of thefe bodies forms a large the circulation of the fap. Some contend, that it returns to the root betwixt the bark and wood. But Hales, bag. Thefe bags contain a third parenchyma, which is a who has made many accurate experiments on the fubjedt, cluder of fmaller bags, didinft and unconnedted with has fliown, that it does not circulate, but afcends and each other, having a fmall dalk by which they are fixed defcends in the fame veffels; that it afcends in hot weato the large bag. Within each of thefe fmall bags are ther, and defcends in cold, like the fpirits in a thermomany hundreds of bladders, compofed of extremely mi- meter. nute fibres. Thefe bladders contain the acid juice of Vegetables begin to abforb fap about the beginning of Spring, and foon after Ihoot out their buds, leaves, and the lemon. From this fliort fketch of the drudhire and compofi- flowers. tion of vegetables, both the farmer and .philofopher may When plants are in a (late of vegetation, efpecially in draw very ufeful and important conclufions. Some of hot weather, there is a great deal of fuperfluous fap abthem will perhaps be taken notice of in the courfe of this forbed; but the fuperfluous parts are carried off by trantreatife. fpiration. Every part of a plant tranfpires; but the greateft quantity paffes by the leaves. Plate V. Fig. 3. A longitudinal fedtion of a le- Some have afligned the tranfpiration of plants, as the caufe of the motion of the fap. It is undoubtedly one '. mbn. AAA, The rind with the vef- caufe of this motion; becaufe, if the tranfpiration be fels that contain the effential 'flopped, at a time when all the veffels are full, the motion of the fap me ft flop of courfe. But then there is a j oil. B 13, The fubftance correfpond- previous and principal caufe, viz. that power in the vefVol. I. No. 2. 3 M fels.
 * but as it afcends into the other parts of the plant,