the Skin of the Seed. Through this Aperture the Root paffes, and fhoots into the Earth feveral Fibres, which are fo many Canals for the Conveyance of the Sap into the Body of the Root, from whence it rifes into the Trunk, and gives it its Elevation in the Air. If the Trunk meets with a Mafs of very compact Earth, it turns afide into another Direction, being unable to pierce through the first Obstruction, and fometimes burfts and dies, for want of Force to proceed further: On the contrary, if it bears against Earth that is light and foft, and which Qualities it ought to receive from the Labour of the Gardener *, it then pursues its Way without any Impediment. The Lobes, after they have exhaufted themselves for the Benefit of the young Plant, extract a Nourishment for themfelves, and then wither away: The fame Fate attends the feminal Leaves, which, by the Ministration of their Pores, imbibe, from the Air, a genial Humidity, and a Flow of Spirits that are falutary to the Plant, and when their Services are compleated, they fade, and die away. The young Plant, by the Inftrumentality of its Root and Fibres, draws from the Earth more ftrong and copious Juices than it was at first fupplied with by the Seed; it faftens it more and more, and begins to unfold its different Parts, that before were rolled up, and involved in one another. Let us now proceed to the Parts within. The Pith, which is a Syftem of little Cells, feparated by Interftices The Pith. or Partitions of a very thin Tex ture, is lodg'd in the Heart of the Trunk and Branches; and there great Quantities of Sap are difcover'd. *Hoc imitatur arando. Virgil. Georg. z. Round Round the Pith a Multitude of The Wood. hollow Fibres rife in lateral Ranges, difpofed in Packets one against another. All thefe Packets afcend the whole Length of the Plant, and are compacted together by feveral Fibres, paffing, in an oblique Direction, from one Range to another, and frequently crof fing each other, like the Figure of an X, or the Meshes of a large Net, in fuch a Manner, that thefe Fibres frequently admit of Spaces between them, which are fometimes in the Form of Lo zenges, fometimes fquare, but generally oblong. This Syftem of long Tubes, that afcend round the Heart, form what we properly call the Wood, and are appointed to convey the Sap. The Bark. Round the Wood is another Affemblage of hollow Fibres, ranged al most in the fame Manner; and these are called the Bark. There are three Parts to be taken notice of, which differ from one another; the inward Bark, or fine Skin, immediately contiguous to the Wood; the Epidermis, or outward Skin, which is a Net extended over all the exterior Surface of the Tree, and the intermediate Bark, or thick Subftance, between the two preceding Skins. The fine Bark. The fine Bark has a very fingular Ufe in Trees: It feems to be a Collection of little Skins, or a Tiffue of Fibres glewed over one another; the firft inward Round of which difengages itself from the reft in the Spring, and adds a new Circumference to the Wood, through its whole Length. Trees, like Infects and Reptils, have feveral Skins folded over one another, but then Reptiles, and Infects diveft themselves of thefe firft Skins, and entirely quit them, to appear, from Time to Time, in a new Form and another Array; whereas Trees Trees have annually a new Habit, but then it is caft over the preceding, the Bark ferving for a Surtout. It is evident, that the fine Bark furnishes the Tree with the Rounds of Fibres that yearly enlarge its Bulk, because, when the large Bark, with that which is inward, is cut off in any Part, leaving the Wood expofed to View, you must never expect that the Wood will receive any Augmentation there: Both the Bark and the Wood continue their Growth in the adjoining Ports, but the Aperture remains as it was first made, and can only be clofed up in a long Procefs of Time, by the lengthening of the Protuberances formed by the neighbouring Fibres. 'Tis eafy to diftinguish these annual Accretions in Trees; one need only cut a Trunk, or a large Branch, horizontally, to discover the several Circles, or different Degrees of Thickness, round the Heart, and one may infallibly determine the Years of the Tree's Age, by the Number of Circles vifible in the Wood: The last Revolutions are always of a lighter Confiftence, and are called the fappy Parts of the Wood, which are rejected by the Workmen, as too weak to be any Way serviceable to their Purpose. These foft Parts contract a Solidity in the fucceeding Years, they likewife become more compact, and, in no Particular, differ from the real Wood. The Tree, by its perpetual Increase in Strength and Circumference, forces the Fibres of the Bark to ftretch and extend themselves, and the outward Surface fometimes bursts with a furprising Noife; this occafions the Creviffes, which are always enlarging in the external Bark, in Proportion to the Growth of the Tree. We have observed, that the large Bark, as well as the fmall, the fappy Parts, and the real Wood, are com The Sap: pofed |