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.