Of the Motion of the Sap.

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B. The nutricious Sap afcendeth the firft Year of a Plant's Growth by the Veffels of the Pith; after which it becomes dry, and fo continueth. 2. The next Part, through which the Sap rifeth, is the Wood, by the Air Veffels, and that only in the Spring. 3. The third Part, by which it afcends, is the Bark, as beforefaid, the greatest Part of the Year; and this is the general Theory of the Motion of the Sap.

A. But, fince both Root and Branch contain Air Vessels, pray in what Part of the Plant doth the Air firft enter it?

B. The chief Entrance of Air is at the Root, along with the Sap; but it also enters more or lefs at the Trunk, Leaves, &c. Parts of the Plant: The Air, or airy Part of the Sap, being thus raifed in its proper Veffels, is filtred through the fame into the Veficles of the parenchymous Infertions in the Wood; and thus is diftributed through all the Parts of the Plant or Tree.

A. Pray why are the Stalks of fome Plants hollow within?

B. Partly for the more expedient Ripening of the Fruit or Seed, which is better effected by a more plentiful Supply of Air by thefe hollow Trunks; and partly for the better determining the true Age of the Plant; for the Air in this Hollow, by drying up the Sap, fhrinketh the Sap Veffels fo far as to hinder the Motion of the Sap S there

therein; whence the Plant must perish of Course Hence it is, that the greater Part of annual Trunks are hollow.

A. Please next to fay, whence the Form or Figuration of the Trunks of Plants and Trees proceeds?

B. Chiefly from the Air in the Air Veffels: Thus almost all Shrubs have a greater Number of Air Veffels, and thofe of a fmaller Size; which therefore most easily yielding to the magnetick Attraction of the external Air, do confequently spread much abroad: By which Spreading the Air Vessels do fooner, and more eafily ftrike into the Bark, and fo produce collateral Budds and Branches, and that upon the first Rifing of the Plant from the Root; and thus it becomes a Shrub: But, if the faid Air Veffels are very large, as in Oak, Walnut, Elm, &c. they will not fo eafily yield or shoot our collaterally; and fo the Trunk grows up taller and more entire.

A. Pray why do fome Trees run up fo very flender, and others fo very thick and big?

B. This is from the Pofition of the Air Veffels; for where they lie moft circular round the Center, in Form of Rings, as in Elm and Afh, there the Tree in proportion grows more tall and taper, and lefs thick: But the faid Veffels fpread more broad, and are poftured in Lines from the

Center,

The Make and Texture of Plants. 259

Center, as in Oak, &c. then the Tree grows very thick; in this Cafe the diametrical Growth of the Wood being more promoted than in any other: For which general Reason alfo Trees grow round or angular.

A. Pray how comes it to pafs, that feveral Stalks of Plants have Joints or Knots? And what is their Ufe?

B. Because in forming the Branch or Blade, both the cortical and lignous Subftance thereof are, upon their fhooting forth, divaricated from their perpendicular Pofture, to a crofs Pofition, and as they with the other grow and thrive together, they bind and throng each other into a Knot. The Ufes of Knots are two, viz. for ftrengthning the Stem; and for finer Growth; for the Knots ferve to ftrain and tranfmit the Juices more refined to the upper Parts, and to the Fruit.

A. How do you account for the Production and Texture of the Leaves?

;

B. The Parts of the Leaf are fubftantially the fame with thofe of the Branch its Skin is the Continuation of that of the Branch; the Fibres or Nerves difperfed through the Leaf, are only Ramifications of the Branch's Wood, or lignous Body; the parenchymous Subftance, which lies between the Fibres, is nothing but the Continuation of the cortical Body,' or Subftance of the Bark, fpread through the fame. S 2

4. Pray

A. Pray what is the Ufe of Leaves?

B. First, for Protection which they afford to each other, and to the Flower in the Bud; as alfo to the Fruit it self in fome Plants. Secondly, for Augmentation; for the Capacity for the due Spreading and Ampliation of a Tree or Plant are its Leaves. Thirdly, they ferve to the greater Purity and Preparation of the Sap; the grofer Parts of which, are retained in the Leaves, while the more elaborate and effential are fupplied to the Flower, Fruit, and Seed, as their proper Aliment. Fourthly, They serve to Perfpiration; for thofe Orifices, obferved to be in Leaves, perform the fame Functions in Trees as the Pores of the Body do in Men; that is, to cause an invifible Perfpiration in Plants.

A. Pray what do you obferve concerning the Flowers of Plants?

B. In the Flower may be observed: 1. The Empalement, or Calyx, or the Cup, which containeth the Flower, and is defigned for the Guard and Security of the other Parts of the Flower. 2. The Foliation, or Compofure of Leaves, which are of divers Forms and Colours; whofe conftituent Parts are the fame as thofe of the Leaves, vix. Skin, Parenchyma, and Air, and Sap Veffels. 3. Within the Foliage ftands the Attire; that is, thofe fine upright Stems with their Apices, and the Stile in the very

Middle

Of Flowers, and Fruit.

261

Middle of all; and these are the general Parts of which the Flower doth confift.

A. Pray can you tell the Ufes of those feveral Parts of the Flower?

B. The Empalement, as I faid, is for the Security of the Flower in Embryo, and afterwards for the Support of the Foliage, to keep the Leaves of the Flower in due and decorous Pofture, which would otherwife hang uncouth and taudry, as a Lady without her Bodice. The Foliage, or Leaves of the Flower, defend the Attire, and in fome Plants the Fruit; it alfo ferves for the further Refining and Separation of proper Parts of the Sap for the perfecting the Seed. The Attire is an Ornament and Diftinction in Flowers. It fupplies alfo divers Kinds of fmall Animals with Food, which harbour therein; that is, in the Hollowness of the Stile. Laftly, it is fuppofed, it alfo ferveth as a Male Sperm to impregnate and fructify the Seed.

A. What is the Nature and Compofition of Fruit, I pray you?

B. The general Nature and Compofition of all Fruit is one and the fame; that is, their effential and truly vital Parts are in all the fame; and but the Continuation of those which I have already obferved to you do conftitute the other Parts of the Plant. But, by the different Conftitution and Textures of thefe Parts, divers confiderably