In which growth, a proportion in length and breadth is requisite: which being rated by the benefit of the Plant, both for firm standing and sufficient Sap, must therefore principally be in length. And because it is thus requisite, therefore by the constitution of one of its Parts, sc. the Lignous Body, it is also made necessary. For the Pores hereof, in that they are all extended by its length, the Sap also according to the frame and site of the said Pores will principally move; and that way as its Sap moves, the same way will the generation of its Parts also proceed; sc. by its length. And the Lignous Body first (that is, by a priority causal) moving in length it self; the Cortical also moves therewith. For that which is nourish’d, is extended; but whatever is extended, is mov’d; that therefore which is nourish’d, is mov’d: The Lignous Body then being first nourish’d, ’tis likewise first mov’d, and so becomes and carries in it the Principle of all Vegetative motion in the Cortical; and so they both move in length.
Yet as the Lignous Body is the Principle of Motion in the Cortical; so the Cortical is the Moderator of that in the Lignous: As in Animal Motions, the Principle is from the Nerves; yet being once given to the Muscle or Limb, and that moving proportionably to its structure, the Nerves also are carried in the same motion with it. We suppose therefore, that as the principal motion of the Lignous Body is in length, so is its proper tendency also to ascend: But being much exceeded both in Compass and Quantity by the Cortical as in the smaller parts of the Root it is; it must needs therefore be over-born and governed by it; and so, though not lose its motion, yet make it that way wherein the Cortical Body may be more obedient to it; which will be by descent: Yet both of them being sufficiently pliable, they are thus capable, where the Soyl I may oppose a direct descent, there to divert any way where it is more penetrable, and so to descend obliquely. For the same reason it may also be, that though you set a Bean with the Radicle upward; yet the Radicle, as it shoots, declining also gradually, is thus arch’d in form of an Hook, and so at last descends. For every declination from a perpendicular Line, is a mixed motion betwixt Ascent and Descent; as that of the Radicle also is, and so seeming to be dependent upon the two contrary Tendencies of the Lignous and Cortical Bodies. What may be the cause of those Tendencies (being most probably external, and perhaps something of a Magnetisme) is besides my Task here to enquire.
Now although the Lignous Body, by the position and shape of its Pores, principally groweth in length; yet will it in some degree likewise in breadth: For it cannot be supposed that the purest Sap is all received into the said Pores; but that part thereof likewise, staying about its Superficial parts, is there tinctur’d and agglutinated to them. And because these Pores are prolonged by its length; therefore is it much more laxe and easily divisible that way; as in slitting a Stick, or cleaving of Timber, and in cutting and hewing them athwart is also seen. Whence it comes to pass, that in shooting from the Center towards the Circumference, and there finding more room, its said original Laxity doth easily in divers places now become greater, and at length in open Partments plainly visible. Betwixt which Partments, the cortical Body, being bound in on the one hand, by the surrounding Skin and Moulds, and pressed upon by the Lignous on the other, must needs insert it self, and so move contrary to it, from the Circumference towards the Center: where the said contrary motions continued as begun, they at last meet, unite, and either make or augment the Pith. And thus the Root is fram’d, and the Skin, the cortical and Lignous Bodies, so as is said, hereunto concurrent. We shall next shew the use of the two other Parts, sc. the Insertment and Pith; and first of the Pith.
One true use of the Pith is for the better Advancement of the Sap, whereof we shall speak in [the next Chapter]. The use we here observe is for the quicker and higher Fermentation of the Sap: For although the Fermentation made in the Cortical Body was well subservient to the first Vegetations, yet those more perfect ones in the Trunk which after follow, require a Body more adapted to it, and that is the Pith; which is so necessary, as not to be only common to, but considerably large in the Roots of most Plants; if not in their inferiour parts, yet at their tops. Where though either deriv’d or amplify’d from the Cortical Body, yet being by its Insertions only, we may therefore suppose, as those, so this, to be more finely constituted. And being also from its co-arctation, while inserted, now free; all its Pores, upon the supply of the Sap, will more or less be amplified: Upon which accounts, the Sap thereinto received, will be more pure, and its fermentation therein more active. And as the Pith is superiour to the Cortical Body by its Constitution, so by its Place. For as it thus stands central, it hath the Lignous Body surrounding it. Now as the Skin is the Fence of the Cortical Body, and that of the Lignous; so is the Lignous again a far more preheminent one unto the Pith; the Sap being here a brisk Liquor, tunn’d up as in a wooden Cask.
And as the Pith subserves the higher Fermentation of the Sap; so do the Insertions its purer Distribution; that separation which the parts of the Sap, by being fermented in the Pith, were dispos’d for; being, upon its entrance into the Insertions, now made: So that as the Skin is a Filtre to the Cortical Body, so are the Insertions a more preheminent one to the Lignous; and as they subserve the purer, so the freer and sufficient distribution of the Sap: For the Root enlarging, and so the Lignous Body growing thicker, although the Cortical and the Pith might supply Sap sufficient to the nutrition of its Parts next adjacent to them; yet those more inward, must needs be scanted of their Aliment; and so, if not quite starv’d, yet be uncapable of equal growth: Whereas the Lignous Body being through its whole breadth frequently disparted, and the Cortical Body inserted through it; the Sap by those Insertions, as the Blood by the disseminations of the Arteries, is freely and sufficiently convey’d to its intimate Parts, even those which from either the cortical Body or the Pith are most remote. Lastly, as the consequent hereof, they are thus assistant to the Latitudinal growth of the Root; as the Lignous Body to its growth in length; so these Insertions of the Cortical, to its better growth in breadth.
Having thus seen the solitary uses of the Several Parts of the Root, we shall lastly propound our Conjectures of that Design whereto they are all together concurrent, and that is the Circulation of the Sap: For the Sap moving through the cortical Body, towards the Pith, through the Insertions thereinto, obtains a pass: Which passage, the superiour Insertions will not favour; because the Pith standing in the same height with them, is there large, the fermenting and course of the Sap quick, and so its opposition strong. But through the inferiour it will much more easily enter; because there, through the smalness of the Pith, the opposition is little, and through the shortness of the Insertions, the way more open. So that though the Sap may meet with some opposition even here, yet here meeting with the least, here it will bestow it self (feeding the Lignous Body in its passage) into the Pith. Into which fresh Sap still entring, this, yet but crude, will subside: that first received and so become a Liquor higher wrought, will more easily mount upwards; and moving in the Pith, as in the Arteria magna, in equal altitude with the more superiour Insertions; the most volatile parts of all will still continue their direct ascent towards the Trunk. But those of a middle nature, and, as not apt to ascend, so being lighter than those beneath them, not to descend neither; they will tend from the Pith towards the Insertions in a motion betwixt both; through which Insertions (feeding the Lignous Body in its passage) it is, by the next subsequent Sap, discharged off into the cortical Body, as into the Vena cava, back again. Wherein, being still pursu’d by fresh Sap from the Center, and more occurring from the Circumference, towards the inferiour Insertions it thus descends; through which, together with part of the Sap afresh imbib’d from the Mould, it re-enters the Pith. From whence, into the Cortical Body, and from thence into the Pith, the cruder part thereof reciprocally is disburs’d; while the most Volatile, not needing the help of a Circulation, more directly ascendeth towards the Trunk.
CHAP. III.
Of the Trunk.
Having thus declar’d the degrees of Vegetation in the Root; the continuance hereof in the Trunk shall next be shew’d: in order to which, the Parts whereof this likewise is compounded, we shall first observe.