Part 4

Upon farther Enquiry, I likewise find, that the Pores of the _Lignous Body_ in the _Trunk_ of Plants, which at first only supposed, by the help of good Glasses are very fairly visible; each Fibre being perforated by 30, 50, 100, or hundreds of Pores. Or what I think is the truest notion of them, that each Fibre, though it seem to the bare eye to be but one, yet is indeed a great number of Fibres together; every Pore being not meerly a space betwixt the several pores of the Wood, but the Concave of a Fiber: So that if it be asked, what all that part of a Vegetable, either Plant or Tree, which is properly call’d the woody part; what all that is, I suppose, that is nothing else but a Cluster of innumerable and most extraordinary small Vessels or concave Fibres. See _Fig. 15_.

Next the Insertions of the _Cortical Body_, which in the _Trunk_ of a Tree saw’d athwart, are plainly discerned as they run from the Circumference toward the Center; the whole Body of the Tree being visibly compounded of two distinct Substances, that of the several Rings, and that of the Insertions, running cross; shewing that in some resemblance in a Plain, which the Lines of Latitude and of the Meridian do in a Globe. See _Fig. 16_.

These Insertions are likewise very conspicuous in Sawing of Trees length-wayes into Boards, and those plain’d, and wrought into Leaves for Tables, Wainscot, Trenchers, and the like. In all which, as in course Trenchers made of _Beech_, and Tables of Oak, there are many parts which have a greater smoothness than the rest; and are so many inserted pieces of the _Cortical Body_; which by reason of those of the _Lignous_, seem to be discontinuous; although in the _Trunk_ they are extended throughout its Breadth.

These Insertions, although as is said, of a quite distinct substance from the _Lignous Body_, and so no where truly incorporated with it, yet being they are in all parts, the one as the Warp, the other as the Woof, mutually braced and inter-woven together, they thus constitute one strong and firmly coherent Body.

As the Pores are greater or less, so are the Insertions also: To the bare eye usually the greater only are discernable: But through an indifferent _Microscope_ there are others also, much more both numerous and small, distinctly apparent. So that, I think, we may observe, that as the grand _Pith_ of the _Trunk_ communicates with, and is augmented by the greater Insertions; so is the _Pith_ of each greater Pore originated from the less; and those (at least) pithy parts in the Midling Pores, from others still less; and suppose, that the least of all are so far intruded into the smallest Pores, as only just to cause a kind of roughness on their concave sides, and no more; to what end shall be said. See _Fig. 17_.

In none of all these Pores can we observe any thing which may have the true nature and use of Valves, which is easily to admit that, to which they will by no means allow a regress. And their non-existence is enough evident, from what in the first Chapter we have said of the _Lobes_ of the _Seed_: in whose _Seminal Root_, were there any _Valves_, it could not be, that by a contrary course of the _Sap_, they should ever grow; which yet, where-ever they turn into Dissimilar Leaves, they do. Or if we consider the growth of the _Root_, which oftentimes is upward and downward both at once.

The Insertions here in the _Trunk_ give us likewise a sight of the position of their Pores. For in a plained piece of Oak, as in Wainscot, Tables, _&c._ besides the larger Pores of the _Lignous Body_, which run by the length of the _Trunk_; the Tract likewise of those of the Insertions may be observed to be made by the breadth, and so directly cross. Nor are they continuous as those of the _Lignous Body_, but very short, as those both of the _Cortical Body_ and _Pith_, with which the Insertions, as to their substance are congenerous. Yet they all stand so together, as to be plainly ranked in even Lines or Rows throughout the breadth of the _Trunk_: As the Tract of these Pores appear to the naked Eye, see in _Fig. 18_. By the best Microscope I have at hand, I can only observe the Ranks of the Pores; not the Pores themselves, saving here and there one; wherefore I have not describ’d them.

The Pores of the _Pith_ likewise being larger here in the _Trunk_, are better observable than in the _Root_: the width whereof, in comparison with their sides so exquisitely thin, may by an Honey-Comb be grosly exemplified; and is that also which the vast disproportion betwixt the Bulk and weight of a dry _Pith_ doth enough declare. In the _Trunks_ of some Plants, they are so ample and transparent, that in cutting both by the length and breadth of the _Pith_, some of them, even to the bare eye would seem to be considerably extended by the length of the said _Pith_; which once I also thought they were, and that only the rest of them were but short and discontinuous, and as ’tis said, somewhat answerable to the Cells of an Honey-Comb. This was the nearest we could come to them, by conjecture, and the assistance of the best Glasses we then had by us, when upon enquiry into the nature of the _Pith:_ But that Worthy Person newly mentioned Mr. _Hooke_ sheweth us, that the Pores of the _Pith_, particularly of _Elder-Pith_, so far as they are visible, are all alike discontinuous; and that the _Pith_ is nothing else (to use his own words) but an heap of Bubbles.

Besides what this Observation informs us of here, it farther confirms what in the second Chapter we have said of the Original of the _Pith_ and _Cortical Body_, and of the sameness of both their natures with the _Parenchyma_ of the Seed. For, upon farther enquiry with better Glasses, I find, that the _Parenchyma_ of the _Plume_ and _Radicle_, and even of the _Lobes_ themselves, though not so apparently, is nothing else but a Mass of Bubbles.

In the _Piths_ of many Plants, the greater Pores have some of them lesser ones within them, and some of them are divided with cross Membranes: And betwixt their several sides, have, I think, other smaller Pores visibly interjected. However, that they are all permeable, is most certain. They stand together not indeterminately, but in even Ranks or Trains; as those of the Insertions by the breadth, so these by the length of the _Trunk_. And thus far there is a general corresponding betwixt the part of the _Root_ and _Trunk_: Yet are there some considerable Disparities betwixt them; wherein, and how they come to pass, and to what especial use and end, shall next be said.

We say then, that the _Sap_ being in the _Root_ by Filtrations, Fermentations (and in what _Roots_ needful, perhaps by Circulation also) duly prepar’d; the prime part thereof passing through the intermediate Coarcture, in due moderation and purity is entertain’d at last into the _Trunk_. And the _Sap_ of the _Trunk_ being purer and more volatile, and so it self apt to ascend; the motion of the _Trunk_ likewise will be more noble, receiving a disposition and tendency to ascend therewith. And what by the _Sap_ the _Trunk_ is in part dispos’d to, by the respective position and quantity of its Parts it is effectually enabled. For whereas in the _Root_ the _Lignous Body_ being in proportion with the _Cortical_, but little, and all lying close within its Center; it must therefore needs be under its controul: on the contrary, being here comparatively of greater quantity, and also more dilated, and having divers of its Branches standing more abroad towards the Circumference, as both in the Leaves and Body of the young _Trunk_ and _Plume_, is seen; it will in its own tendency to ascend, reduce the _Cortical Body_ to a compliance with it.

And the _Trunk_ thus standing from under the restraint of the Mould in the open Air, the disposition of its Parts originally different from that of the Parts in the Root will not only be continued, but improved: For by the force and pressure of the _Sap_ in its collateral Motion, the _Lignous Body_ will now more freely and farther be dilated. And this being dilated, the _Cortical Body_ also, must needs be inserted; and is therefore in proportion alwayes more or less smaller here in the _Trunk_, than in the _Root_. And as the _Cortical Body_ lessens, so the _Pith_ will be enlarged, and by the same proportion is here greater. And the _Pith_ being enlarged it self, its Pores (the _Lignous Body_, upon its dilatation, as it were tentering and stretching out all their sides) must needs likewise be enlarged with it, and accordingly are ever greater in the _Pith_ of the _Trunk_, than of the _Root_. And the dilatation of the _Lignous Body_ still continued, it follows, that whereas the _Pith_ descendent in the _Root_, is not only in proportion less and less, but also in the smaller extremities thereof, and sometimes higher altogether absent: Contrariwise, in the _Trunk_ it is not only continued to its top, but also there in proportion equally ample with what it is in any other inferiour part.

But although the openness of the Ayr permitting be alwayes alike; yet the Energy of the _Sap_ effecting; being different; as therefore that doth, the dilatation of the _Trunk_ will also vary. If that be less, so is this; as in the _Trunks_ of most Trees: If that be greater, so is this; as in Plants is common; the _Lignous Body_ being usually so far dilated, that the _utmost shootings_ thereof may easily be seen to jut out, and adjoyn to the Skin. And if the _Sap_ be still of greater energy, it so far dilates the _Lignous Body_, as not only to amplifie the _Pith_ and all its Pores; but also so far to stretch them out, as to make them tear. Whereupon either running again into the _Cortical Body_, or shrinking up towards it, the _Trunk_ thus sometimes becomes an _hollow Stalk_, the _Pith_ being wholly, or in part voyded. But generally it keeps entire; and where it doth, the same proportion and respect to the _Lignous_ and _Cortical Bodies_, as is said. The Consequences of all which will be, the strength of the _Trunk_, the security and plenty of the _Sap_, its Fermentation will be quicker, its Distribution more effectual, and its Advancement more sufficient.

First, the erect growth and strength of the _Trunk_; this being by the position of its several parts effected: For besides the slendering of the _Trunk_ still towards the top, the Circumferential position of the _Lignous Body_ likewise is, and that eminently hereunto subservient: So that as the _Lignous Body_ in the smaller part of the _Root_ standing Central, we may thence conceive and see their pliableness to any oblique motion; so here, on the contrary, the _Lignous Body_ standing wide, it thus becomes the strength of the _Trunk_, and most advantageous to its perpendicular growth. We see the same Design in _Bones_ and _Feathers_: The strongest _Bones_, as those in the Legs, are hollow. Now should we suppose the same _Bone_ to be contracted into a Solid Body, although now it would be no heavier, and in that respect, as apt for motion; yet would it have far less strength, than as it is dilated to a Circumferential posture. And so for _Quills_, which, for the same Reasons, in subserviency to flight, we see how exceeding light they are, and yet, in comparison with the thinness of their Body, how very strong: We see it not only in Nature, but Art. For hence it is that _Joyners_ and _Carpenters_ unite and set together their Timber-pieces and several Works oftentimes with double Joynts; which, although they are no thicker than a single one might be made, yet standing at a distance, have a greater strength than that could have. And the same Architecture will have the same use in the _Trunks_ of Plants, in most whereof ’tis very apparent; as for instance, in Corn: For Nature designing its _Sap_ a great Ascent for its higher maturity, hath given it a tall _Trunk_; but to prevent its ravenous despoiling either of the Ear or Soyl; although it be tall, yet are its sides but thin: and because again, it should grow not only tall and thriftily, but for avoiding propping up, strongly too; therefore, as its height is over-proportioned to the thinness of its sides, so is its Circumference also; being so far dilated as to parallel a _Quill_ it self. Besides the position of the _Lignous Body_ within the compass of a Ring, we see some shootings thereof often standing beyond the Circumference of the said Ring, making sometimes a triangular, oftner a quadrangular Body of the _Trunk_; to the end, that the Ring being but thin, and not self-sufficient, these, like Splinters to _Bones_, might add strength and stability to it.

Next, the security and plenty of the _Sap_. For should the _Lignous Body_, as it doth in the _Root_, its smaller parts, stand Central here also, and so the _Cortical_ wholly surround it: the greater part of the _Sap_ would thus be more immediately expos’d to the Sun and ayr; and being lodg’d in a laxe Body, by them continually be prey’d upon, and as fast as supplied to the _Trunk_, be exhausted. Whereas the _Pith_ standing in the Center, the _Sap_ therein being not only most remote from the Ayr and Sun, but by the _Barque_, and especially the _Wood_, being also surrounded and doubly immur’d, will very securely and copiously be conveyed to all the Collateral parts, and (as shall be said how) the top of the _Trunk_.

And the _Sap_ by the amplitude, and great porosity of the _Pith_ being herein more copious, its Fermentation also will be quicker; which we see in all Liquors by standing in a greater quantity together, proceeds more kindly: And being tunn’d up within the _Wood_, is at the same time not only secur’d from loss, but all extream mutations, the Day being thus not too hot, nor the Night too cold for it.

And the Fermentation hereof being quicker, its motion also will be stronger, and its distribution more effectual, not only to the dilatation of the _Trunk_, but likewise the shooting out of the Branches. Whence it is, that in the Bodies of Trees, the _Barque_ of it self, though it be sappy, and many Fibres of the _Lignous Body_ mixed with it, yet seldom sendeth forth any; and that in Plants, those with the least _Pith_ (other advantages not supplying this defect) have the fewest or smallest Branches, or other collateral Growths: and that _Corn_, which hath no _Pith_, hath neither any Branches.

Lastly, the Advancement of the _Sap_ will hence also be more ready and sufficient. For the understanding where, and how, we suppose that in all _Trunks_ whatsoever there are two parts joyntly hereunto subservient. In some the _Lignous Body_ and the _Cortical_, as in older _Trunks_, the _Pith_ being either excluded or dried: But in most, principally the _Lignous Body_ and _Pith_; as in most Annual Growths of Trees; but especially Plants, where the _Cortical Body_ is usually much and often wholly inserted.

Of the _Lignous_ body it is so apparent by its Pores, or rather by its Vessels, that we need no farther evidence. For to what end are Vessels but for the conveyance of Liquor? And is that also, which upon cutting the young Branch of a Sappy Tree or Plant, by an accurate and steady view may be observed. But when I say the Pores of the _Lignous Body_, I mean principally them of the younger shootings, both those which make the new Ring, and those which are mixed with the _Cortical Body_ in the _Barque_: that which ascendeth by the Pores of the older Wood, being probably, because in less quantity, more in form of a Vapour, than a Liquor. Yet that which drenching into the sides of its Pores, is with all thereunto sufficient Aliment; as we see _Orpine_, _Onions_, &c. only standing in a moyster Ayr will often grow; And being likewise in part supplied by the Insertions from the younger Shoots: But especially, because as it is but little, so it serveth only for the growth of the said _Older Wood_, and no more; whereas the more copious Aliment ascendent by the younger Shoots, subserves not only their own growth, but the generation of others; and is besides with that in the _Cortical Body_ the Fountain of _Perspirations_, which we know even in Animals are much more abundant than the _Nutritive parts_; and doubtless in a _Vegetable_ are still much more.

But these Pores, although they are a free and open way to the ascending _Sap_; yet that meer Pores or Vessels should be able of themselves to advance the _Sap_ with that speed, strength & plenty, and to that height, as is necessary, cannot probably be supposed. It follows then, that herein we must grant the _Pith_ a joynt service. And why else in the smaller parts of the _Root_, where the _Pith_ is often wanting, are the Pores there greater? Why is the _Pith_ in all primitive growths the most _Sappy_ part, why hath it so great a stock of _Sap_, if not after due maturation within it self still to be disbursed into the Fibres of the _Lignous Body_? Why are the annual growths of all both Plants and Trees with great Piths, the quickest and the longest? But how are the Pores of the _Pith_ permeable? That they are so, both from their being capable of a repletion with _Sap_, and of being again wholly emptied of it, and again, instead thereof fill’d with Ayr, is as certain as that they are Pores. That they are permeable, by the breadth, appears from the dilatation of the _Lignous Body_, and from the production of Branches, as hath been, and shall hereafter be said. And how else is there a Communion betwixt this and the _Cortical Body_? That they are so also, by the length, is probable, because by the best _Microscope_ we cannot yet observ, that they are visibly more open by the breadth, than by the length. And withal are ranked by the length, as those of the Insertions by the breadth of the _Trunk_. But if you set a piece of dry _Elder-Pith_ in some tinged Liquor, why then doth it not penetrate the Pores, so as to ascend through the Body of the _Pith_? The plain reason is, because they are all fill’d with Ayr. Whereas the _Pith_ in a Vegetating Plant, as its Parts or Pores are still generated, they are at the same time also fill’d with _Sap_; which, as ’tis gradually spent, is still repair’d by more succeeding, and so the Ayr still kept out; as in all primitive growths, and the _Pith_ of _Elder_ it self: Yet the same _Pith_, by reason of the following Winter, wanting a more copious and quick supply of _Sap_, thus once become, ever after keeps dry. And since in the aforesaid Trial the Liquor only ascends by the sides of the _Pith_, that is of its broken Pores, we should thence by the same reason conclude that they are not penetrable by the breadth neither, and so no way; and then it need not be ask’d what would follow. But certainly the _Sap_ in the Pores of the _Pith_ is discharged and repaired every moment, as by its shriv’ling up; upon cutting the Plant is evident.

We suppose then, that as the _Sap_ ascendeth into the _Trunk_ by the _Lignous Body_, so partly also by the _Pith_. For a piece of _Cotton_ with one end immers’d in some tinged Liquor, and with the other erect above, though it will not imbibe the Liquor so far as to over-run at the top, yet so as to advance towards it, it will; so here, the _Pith_ being a porous and spongy Body, and in its Vegetating state its Pores also permeable, as a curious Filtre of Natures own contrivance, it thus advanceth, or as people use to say, sucks up the _Sap_. Yet as it is seen of the Liquor in the Cotton; so likewise are we to suppose it of the _Sap_ in the _Pith_; that though it riseth up for some way, yet is their some term, beyond which it riseth not, and towards which the motion of the ascending _Sap_ is more and more broken, weak and slow, and so the quantity thereof less and less. But because the _Sap_ moveth not only by the length, but breadth of the _Pith_; at the same time therefore as it partly ascendeth by the _Pith_, it is likewise in part pressed into the _Lignous Body_ or into its Pores. And since the motion of the _Sap_ by the breadth of the _Pith_ not being far continued, and but collateral, is more prone and easie than the perpendicular, or by its length; it therefore follows, that the collateral motion of the _Sap_, at such a height or part of the _Pith_, will be equally strong with the perpendicular at another part, though somewhat beneath it; and that where the perpendicular is more broken and weak, the collateral will be less; and consequently where the perpendicular tendency of the _Sap_ hath its term, the collateral tendency thereof, and so its pressure into the Pores of the _Lignous Body_ will still continue. Through which, in that they are small, and so their sides almost contiguous, the _Sap_ as fast as pressed into them will easily run up; as betwixt the two halves of a Stick first slit, and then tied somewhat loosely together, may also any Liquor be observed to do. And the sides of the said Pores being not smooth, but by the intrusion of the smallest insertions made somewhat rough; by that means the higher and more facile ascent of the _Sap_ therein will farther be promoted. By all which Advantages the facility and strength of that ascent will be continued higher in the said Pores than in the _Pith_. Yet since this also, as well as that in the _Pith_ will have its term; the _Sap_, although got thus far, would yet at last be stagnant, or at least its ascent be very sparing, slow and feeble, if not some way or other re-inforced. Wherefore, as the _Sap_ moving by the breadth of the _Pith_, presseth thence into the Pores of the _Lignous Body_; so having well fill’d these, is in part by the same Collateral motion disbursed back into a yet higher Region of the _Pith_. By which partly, and partly by that portion of the _Sap_, which in its perpendicular ascent was before lodged therein; ’tis thus here, as in any inferiour place equally repleat. Whereupon the force and vigour of the perpendicular motion of the _Sap_ herein will likewise be renew’d; and so its Collateral motion also, and so its pressure into the Pores of the _Lignous Body_, and consequently its ascent therein; and so by a pressure from these into the _Pith_, and from the _Pith_ into these reciprocally carried on, a most ready and copious ascent of the _Sap_ will be continued from the bottom to the top, though of the highest _Trunk_.

_An Appendix._

_Of Trunk-Roots and Claspers._

The distinct Parts whereof these are constituted, are the same with those of the _Trunk_, and but the continuation of them.

_Trunk-Roots_ are of two kinds: Of the one, are those that vegetate by a direct descent: The place of their Eruption is sometimes all along the _Trunk_; as in _Mint_, &c. Sometimes only at its utmost point, as in the _Bramble_.

The other sort are such as neither ascend nor descend, but shoot forth at right Angles with the _Trunk_; which therefore, though as to their Office, they are true _Roots_, yet as to their Nature, they area _Middle thing_ betwixt a _Root_ and a _Trunk_.

_Claspers_, though they are but of one kind, yet their nature is double; not a mean betwixt that of the _Root_ and that of the _Trunk_, but a compound of both; as in their Circumvolutions, wherein they often mutually ascend and descend, is seen.